Statistical Power

X-ray fluorescence microscopy (XFM) facilitates high-sensitivity quantitative imaging of trace metals at high spatial resolution over large sample areas and can be applied to a diverse range of biological samples. Accurate determination of elemental content from recorded spectra requires proper calibration of the XFM instrument under the relevant operating conditions. Here, we describe the manufacture, characterization, and utilization of multielement thin-film reference foils for use in calibration of XFM measurements of biological and other specimens. We have used these internal standards to assess the two-dimensional distribution of trace metals in a thin tissue section of a rat hippocampus. The data used in this study was acquired at the XFM beamline of the Australian Synchrotron using a new 384-element array detector (Maia) and at beamline 2-ID-E at the Advanced Photon Source. Post-processing of samples by different fixation techniques was investigated, with the conclusion that differences in solvent type and sample handling can significantly alter elemental content. The present study highlights the quantitative capability, high statistical power, and versatility of the XFM technique for mapping trace metals in biological Published in the special issue Imaging Techniques with Synchrotron Radiation samples, e.g., brain tissue samples in order to help understand neurological processes, especially when implemented in conjunction with a high-performance detector such as Maia.

In this article, we consider Bayesian inference procedures to test for a unit root in Stochastic Volatility (SV) models. Unit-root tests for the persistence parameter of the SV models, based on the Bayes Factor (BF), have been recently introduced in the literature. In contrast, we propose a flexible class of priors that is noninformative over the entire support of the persistence parameter (including the non-stationarity region). In addition, we show that our model fitting procedure is computationally efficient (using the software WinBUGS). Finally, we show that our proposed test procedures have good frequentist properties in terms of achieving high statistical power, while maintaining low total error rates. We illustrate the above features of our method by extensive simulation studies, followed by an application to a real data set on exchange rates.

The history of developments in atomic physics and its applications follows the decisive input provided by Maxwell and subsequent discoveries by his successors at the Cavendish Laboratory. In medicine the potential applications of particle physics (with the notable exception of the electron) were unfortunately delayed by the disappointing experiences with neutron therapy, which produced longterm scepticism. Neutrons are not appropriate for cancer therapy because not only their physical dose distributions offer no advantages over X-rays, but also their biological dose distributions are worse. The much improved dose distributions achieved with charged particles offer real prospects for better treatment outcomes because of the large reduction in the volume of unnecessarily irradiated tissue in many situations. Charged particle therapy is relatively new and can be applied with increasing confidence due to advances in radiology and computing, but at present there are insufficient numbers of treatment facilities to produce statistically powerful studies to compare treatment outcomes with those of X-rays. Considerable progress has been achieved in Japan and Germany with pilot studies of carbon ions but their efficacy compared with protons needs to be tested: in theory carbon should be better for intrinsically radio-resistant and for the most hypoxic tumours. The optimisation of proton and ion beam therapy in clinical practice remains to be achieved, but there are good scientific reasons why these modalities will be preferred by patients and their physicians in the future. Regrettably, despite hosting many of the momentous discoveries that enabled the development of charged particle therapy, the UK is slow to adopt and implement this very important form of cancer treatment.

Objective: To evaluate the value of alternative monotherapy versus adjunctive therapy in partial epilepsy refractory to single antiepileptic drug (AED) therapy. Design and methods: In a multicentre, parallel-group, open-label study, patients with cryptogenic or symptomatic partial epilepsy not controlled after single or sequential AED monotherapies were randomised to monotherapy with an alternative AED or to adjunctive therapy with a second AED. The AED to be added/substituted and dose adjustments were determined by the physician's best judgement. Patients were followed up until withdrawal from the allocated treatment or for 12 months, whichever first. Outcome measures included proportion of patients continuing on the assigned treatment strategy, proportion of patients seizure-free after achieving the target maintenance dose, and adverse effects rates. Data were analysed by actuarial life tables, Kaplan-Meier survival analysis and Cox proportional hazard regression model. Results: Of a total of 157 patients (including 94 previously exposed to only one AED), 76 were randomised to alternative monotherapy and 81 to adjunctive therapy. The two groups were balanced in clinical characteristics. The 12-month cumulative probability of remaining on the assigned treatment was 55% in patients randomised to alternative monotherapy and 65% in those randomised to adjunctive therapy (P = 0.74). The 12-month probability of remaining seizure-free was 14 and 16%, respectively (P = 0.74).

Arterial spin labeling (ASL) perfusion fMRI data differ in important respects from the more familiar blood oxygen level-dependent (BOLD) fMRI data and require specific processing strategies. In this paper, we examined several factors that may influence ASL data analysis, including data storage bit resolution, motion correction, preprocessing for cerebral blood flow (CBF) calculations and nuisance covariate modeling. Continuous ASL data were collected at 3 T from 10 subjects while they performed a simple sensorimotor task with an epoch length of 48 s. These data were then analyzed using systematic variations of the factors listed above to identify the approach that yielded optimal signal detection for task activation. Improvements in statistical power were found for use of at least 10 bits for data storage at 3 T. No significant difference was found in motor cortex regarding using simple subtraction or sinc subtraction, but the former presented minor but significantly (Pb.024) larger peak t value in visual cortex. While artifactual head motion patterns were observed in synthetic data and background-suppressed ASL data when label/control images were realigned to a common target, independent realignment of label and control images did not yield significant improvements in activation in the sensorimotor data. It was also found that CBF calculations should be performed prior to spatial normalization and that modeling of global fluctuations yielded significantly increased peak t value in motor cortex. The implementation of all ASL data processing approaches is easily accomplished within an open-source toolbox, ASLtbx, and is advocated for most perfusion fMRI data sets.

This paper tests traditional capital structure models against the alternative of a pecking order model of corporate financing. The basic pecking order model, which predicts external debt financing driven by the internal financial deficit, has much greater timeseries explanatory power than a static tradeoff model, which predicts that each firm adjusts gradually toward an optimal debt ratio. We show that our tests have the power to reject the pecking order against alternative tradeoff hypotheses. The statistical power of some usual tests of the tradeoff model is virtually nil.

Recent developments in ecological statistics have reached behavioral ecology, and an increasing number of studies now apply analytical tools that incorporate alternatives to the conventional null hypothesis testing based on significance levels. However, these approaches continue to receive mixed support in our field. Because our statistical choices can influence research design and the interpretation of data, there is a compelling

Background: Statistical power calculations are a critical part of any study design for gene mapping. Most calculations assume that the locus of interest is biallelic. However, there are common situations in human genetics such as X-linked loci in males where the locus is haploid. The purpose of this work is to mathematically derive the biometric model for haploid loci, and to compute power for QTL mapping when the loci are haploid. Results: We have derived the biometric model for power calculations for haploid loci and have developed software to perform these calculations. We have verified our calculations with independent mathematical methods. Conclusion: Our results fill a need in power calculations for QTL mapping studies. Furthermore, failure to appropriately model haploid loci may cause underestimation of power.

Coronary artery bypass grafting (CABG) is an established revascularization procedure for the treatment of advanced atherothrombotic coronary artery disease.1 The National Center for Health Statistics estimated that 427,000 procedures were performed on 249,000 patients in the ...

A potentially serious disadvantage of association mapping is the fact that marker-trait associations may arise from confounding population structure as well as from linkage to causative polymorphisms. Using genome-wide marker data, we have previously demonstrated that the problem can be severe in a global sample of 95 Arabidopsis thaliana accessions, and that established methods for controlling for population structure are generally insufficient. Here, we use the same sample together with a number of flowering-related phenotypes and data-perturbation simulations to evaluate a wider range of methods for controlling for population structure. We find that, in terms of reducing the falsepositive rate while maintaining statistical power, a recently introduced mixed-model approach that takes genomewide differences in relatedness into account via estimated pairwise kinship coefficients generally performs best. By combining the association results with results from linkage mapping in F2 crosses, we identify one previously known true positive and several promising new associations, but also demonstrate the existence of both false positives and false negatives. Our results illustrate the potential of genome-wide association scans as a tool for dissecting the genetics of natural variation, while at the same time highlighting the pitfalls. The importance of study design is clear; our study is severely under-powered both in terms of sample size and marker density. Our results also provide a striking demonstration of confounding by population structure. While statistical methods can be used to ameliorate this problem, they cannot always be effective and are certainly not a substitute for independent evidence, such as that obtained via crosses or transgenic experiments. Ultimately, association mapping is a powerful tool for identifying a list of candidates that is short enough to permit further genetic study.

To effectively evaluate medical literature, practicing physicians and medical researchers must understand the impact of statistical tests on research outcomes. Applying inefficient statistics not only increases the need for resources, but more importantly increases the probability of committing a Type I or Type II error. The t-test is one of the most prevalent tests used in the medical field and is the uniformally most powerful unbiased test (UMPU) under normal curve theory. But does it maintain its UMPU properties when assumptions of normality are violated? A Monte Carlo investigation evaluates the comparative power of the independent samples t-test and its nonparametric counterpart, the Wilcoxon Rank-Sum (WRS) test, to violations from population normality, using three commonly occurring distributions and small sample sizes. The t-test was more powerful under relatively symmetric distributions, although the magnitude of the differences was moderate. Under distributions with extreme skews, the WRS held large power advantages. When distributions consist of heavier tails or extreme skews, the WRS should be the test of choice. In turn, when population characteristics are unknown, the WRS is recommended, based on the magnitude of these power differences in extreme skews, and the modest variation in symmetric distributions. J CLIN EPIDEMIOL 52;3:229-235, 1999.

Survival analysis statistics have been used to estimate shelf life of foods based on consumers' acceptance or rejection of samples with different storage times. The interval censored nature of the data does not allow regular methods to estimate the number of necessary consumers (N) for these studies. The objective of the present work was to use simulation studies to estimate N considering the error in the estimation, statistical significance and statistical power. Based on previous studies a Weibull model was assumed for the lifetime distribution with a shape parameter r between 0.17 and 0.71. Simulations were calculated supposing shelf-life values in the middle range of an adimensional time scale. Graphs to estimate N under different scenarios are presented. Considering the average r, an alpha value (Type I error) of 5%, a beta value (Type II error) of 20%, the shelf life to be in the middle of the studied time range, and a difference between the true shelf life and the estimated shelf life of 0.5 on a 0-6 time scale, gave an N value of 120 consumers for this particular set of parameters.

A nonsignificant result may be obtained in a study despite that there is an ecologically important and strong effect and difference. This lack of significance may be due to a small sample size and low statistical power of the test. Therefore an adequate sample size is required for accurately estimating and comparing vegetation characteristics and obtaining an acceptable power for the test. This paper presents sample size equations and explains, with examples, how to use the equations for estimating vegetation quantitative characteristics, proportion tests, comparing between two independent samples and two paired samples, correlation analysis, simple and multiple linear regression and logistic regression, chi-square test using contingency tables and analysis of variance (ANOVA).

Survival analysis statistics have been used to estimate shelf life of foods based on consumers’ acceptance or rejection of samples with different storage times. The interval censored nature of the data does not allow regular methods to estimate the number of necessary consumers (N) for these studies. The objective of the present work was to use simulation studies to estimate

Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have begun to describe the functional neuroanatomy of emotion. Taken separately, specific studies vary in task dimensions and in type(s) of emotion studied and are limited by statistical power and sensitivity. By examining findings across studies, we sought to determine if common or segregated patterns of activations exist across various emotional tasks. We reviewed 55 PET and fMRI activation studies (yielding 761 individual peaks) which investigated emotion in healthy subjects. Peak activation coordinates were transformed into a standard space and plotted onto canonical 3-D brain renderings. We divided the brain into 20 nonoverlapping regions, and characterized each region by its responsiveness across individual emotions (positive, negative, happiness, fear, anger, sadness, disgust), to different induction methods (visual, auditory, recall/imagery), and in emotional tasks with and without cognitive demand. Our review yielded the following summary observations: (1) The medial prefrontal cortex had a general role in emotional processing; (2) fear specifically engaged the amygdala; (3) sadness was associated with activity in the subcallosal cingulate; (4) emotional induction by visual stimuli activated the occipital cortex and the amygdala; (5) induction by emotional recall/imagery recruited the anterior cingulate and insula; (6) emotional tasks with cognitive demand also involved the anterior cingulate and insula. This review provides a critical comparison of findings across individual studies and suggests that separate brain regions are involved in different aspects of emotion. © 2002 Elsevier Science (USA)

We assessed scientists' ability to detect declines of marine mammal stocks based on recent levels of survey effort, when the actual decline is precipitous. We defined a precipitous decline as a 50% decrease in abundance in 15 yr, at which point a stock could be legally classified as "depleted" under the U.S. Marine Mammal Protection Act. We assessed stocks for three categories of cetaceans: large whales (n = 23, most of which are listed as endangered), beaked whales (n = 11, potentially vulnerable to anthropogenic noise), and small whales/dolphins/porpoises (n = 69, bycatch in fisheries and important abundant predators), for two categories of pinnipeds with substantially different survey precision: counted on land (n = 13) and surveyed on ice (n = 5), and for a category containing polar bear and sea otter stocks (n = 6). The percentage of precipitous declines that would not be detected as declines was 72% for large whales, 90% for beaked whales, and 78% for dolphins/porpoises, 5% for pinnipeds on land, 100% for pinnipeds on ice, and 55% for polar bears/sea otters (based on a one-tailed t-test, ␣ = 0.05), given the frequency and precision of recent monitoring effort. We recommend alternatives to improve performance.

The Coral Reef Assessment and Monitoring Program (CRAMP) of Hawai'i was established in 1998 to monitor long-term changes in coral reef benthic communities around the state. Development of the methodology involved analysis of results from previous monitoring programs in Hawai'i to determine precision and statistical power of various methods to detect change. Additional field trials were conducted to examine factors such as repeatability, appropriate transect length, number of transects, number of samples per transect, cover estimation techniques, observer variation, as well as time and financial constraints. Benthic monitoring methods used previously in Hawai'i generally showed low statistical power for detecting change due to low precision and small sample size. Field trials indicated that repeatability of conventional techniques using transects or quadrats had high variation and consequently low statistical power unless efforts were made to reposition the sampling units with greater precision. Longer transects (e.g., 25 and 50 m) had higher variability than shorter transects (e.g., 10 m), suggesting that smaller sampling units were more appropriate for the habitats sampled. Variability among observers analyzing the same data was low in comparison with other sources of error. Visual estimation techniques showed low initial cost but were inefficient per survey. Digital video required the highest initial monetary investment but yielded the greatest quantity of data per survey with sufficient quality. The cost effectiveness of the digital video method compared with other techniques increased with more surveys and in more remote situations where logistical expenses were incurred. A within-habitat stratified random sampling design was implemented for the CRAMP design. Fixed transects were chosen to reduce temporal variance and allowed efficient resurveying under the high-wave-energy field conditions typically found in Hawai'i. The method was designed to detect an absolute change of 10% in benthic cover with high statistical power using 50 points per frame, 20-30 frames per transect, and 8-10 transects per depth. Fixed photoquadrats with high precision and high resolution were included in the design to allow detailed monitoring of coral/algal growth, recruitment, and mortality. 145

Well-Being: Method, Mode, and Measurement Effects. 2006. Social Science Research 35) tested one key aspect of the validity of Ryff's six-factor model of psychological well-being (RPWB), namely, whether there is substantial independent variation among the six factors. In several large and heterogeneous samples, under a variety of model specifications, and using various sets of RPWB items, we found very high factor correlations among the dimensions of well-being, especially personal growth, purpose in life, self-acceptance, and environmental mastery. That is, the six-factor model makes theoretical claims that do not yield large or consistent empirical distinctions when standard measures and instrumentation are used. Where Ryff and Singer's comment (Best News Yet on the Six-Factor Model of Well-Being. 2006. Social Science Research 35) refers directly to that analysis, their methodological discussion is most often irrelevant or incorrect. Their text largely ignores and fails 0049-089X/$ -see front matter Ó

This work tackles the problem of whether the dissociation between two performances in a single-case study should be computed as the difference between the raw or between the standardized (e.g. z) scores. A wrong choice can lead to serious inflation of the probability of finding false dissociations and missing true dissociations. Two common misconceptions are that (i) standardized scores are a universally valid choice, or (ii) raw scores can be subtracted when the two performances concern the same "task/test", otherwise standardized scores are better. These and other rules are shown to fail in specific cases and a solution is proposed in terms of in-depth analysis of the meaning of each score. The scores that should be subtracted are those that better reflect "deficit severities"the latent, unobservable degrees of damage to the cognitive systems that are being compared. Thus explicit theoretical modelling of the investigated cognitive function(s)-the "scenario"-is required. A flowchart is provided that guides such analysis, and shows how a given neuropsychological scenario leads to the selection of an appropriate statistical method for detecting dissociations, introducing the critical concept of "deficit equivalence criterion"-the definition of what exactly a non-dissociation should look like. One further, overlooked problem concerning standardized scores in general (as measures of effect size, of which neuropsychological dissociations are just one example) is that they cannot be meaningfully compared if they have different reliabilities. In conclusion, when studying dissociations, increases in false-positive and false-negative risks are likely to occur when no explicit neuropsychological theory is offered that justifies the definition of what are to be considered as equivalent deficit severities in both performances, and which would lead to appropriate selection of raw, standardized, or any other type of score. More generally, the choice of any measure in any research context needs explicit theoretical modelling, without which statistical risks cannot be controlled.

One of the causes of the underuse of the Solomon four-group design may be that the complete details for the statistical analysis have not previously been presented. The primary issue previously unaddressed was how to combine an analysis of the effect of the treatment in the posttest-only groups with the same effect in the pre-and posttest groups (after an earlier phase of the analysis has shown no evidence of pretest sensitization.) A meta-analytic solution for this problem is proposed, and the entire analysis is presented, complete with flowchart and example. It is shown that the analysis has adequate statistical power even if the total N is not increased from that of a posttest-only design, removing the last of the serious objections to the Solomon design.

Objectives: To describe a method using confidence intervals (CIs) to estimate the sample size for a pilot randomized trial. Study Design: Using one-sided CIs and the estimated effect size that would be sought in a large trial, we calculated the sample size needed for pilot trials.

This chapter summarizes the principles of fractionated radiotherapy and altered fractionation approaches. Clinical reirradiation examples and isoeffect calculations are provided. The vast majority of published reirradiation series consist of retrospective data or small prospective studies with limited statistical power. In addition, the typical patient populations are more heterogeneous than in first-line radiotherapy studies. For example, patients with local relapse, regional relapse, or second primary tumors might be included. Therefore, the level of evidence is not comparable to that of first-line radiotherapy, where many treatment recommendations and guidelines are based on large and well-designed prospective randomized trials or meta-analyses of several trials. Reirradiation is often used for palliative symptoms but occasionally curative approaches, which require high total radiation doses, might be possible. Hyperfractionated reirradiation might theoretically improve the therapeutic ratio, but prospective trials are required to confirm this hypothesis.

Colorectal cancer is one of the most common internal malignancies in Western society. The cause of this disease appears to be multifactorial and involves genetic as well as environmental aspects. The human colon is continuously exposed to a complex mixture of compounds, which is either of direct dietary origin or the result of digestive, microbial and excretory processes. In order to establish the mutagenic burden of the colorectal mucosa, analysis of specific compounds in feces is usually preferred. Alternatively, the mutagenic potency of fecal extracts has been determined, but the interpretation of these more integrative measurements is hampered by methodological shortcomings. In this review, we focus on exposure of the large bowel to five different classes of fecal mutagens that have previously been related to colorectal cancer risk. These Ž . Ž . include heterocyclic aromatic amines HCA and polycyclic aromatic hydrocarbons PAH , two exogenous factors that are Ž . predominantly ingested as pyrolysis products present in food and partially excreted in the feces. Additionally, we discuss Ž . N-nitroso-compounds, fecapentaenes and bile acids, all fecal constituents mainly of endogenous origin. The mutagenic and carcinogenic potency of the above mentioned compounds as well as their presence in feces, proposed mode of action and potential role in the initiation and promotion of human colorectal cancer are discussed. The combined results from in vitro and in vivo research unequivocally demonstrate that these classes of compounds comprise potent mutagens that induce many different forms of genetic damage and that particularly bile acids and fecapentaenes may also affect the carcinogenic process by epigenetic mechanisms. Large inter-individual differences in levels of exposures have been reported, including those in a range where considerable genetic damage can be expected based on evidence from animal studies. Particularly, however, Ž . exposure profiles of PAH and N-nitroso compounds NOC have to be more accurately established to come to a risk evaluation. Moreover, lack of human studies and inconsistency between epidemiological data make it impossible to describe colorectal cancer risk as a result of specific exposures in quantitative terms, or even to indicate the relative importance of the mutagens discussed. Particularly, the polymorphisms of genes involved in the metabolism of heterocyclic amines are important determinants of carcinogenic risk. However, the present knowledge of gene-environment interactions with regard to colorectal cancer risk is rather limited. We expect that the introduction of DNA chip technology in colorectal cancer epidemiology will offer new opportunities to identify combinations of exposures and genetic polymorphisms that relate to increased cancer risk. This knowledge will enable us to improve epidemiological study design and statistical power in future research. q 1 Manuscript requested by Paul A. White. 1383-5742r00r$ -see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 1 3 8 3 -5 7 4 2 0 0 0 0 0 0 3 -X ( ) T.M.C.M. de Kok, J.M.S.

Recently it was shown that the design changes from the ABG-I to ABG-II hip stem resulted in a better, although not significant, proximal bone preservation. Our hypothesis was that by matching patients for preoperative bone quality, statistical power would increase and that the trend of better proximal bone preservation in ABG-II might become significant. Twenty-four ABG-II patients were compared to two different ABG-I groups: (1) 25 patients from our earlier prospective study and (2) a group of 24 patients selected to perfectly match the ABG-II group regarding gender, age and preoperative bone quality. Postoperative changes in periprosthetic bone mineral density (BMD) were quantified at 2 years postoperatively using DEXA scanning. Bone preservation (less BMD loss) was better for the ABG-II than the ABG-I (all two groups) in the proximal zones 1 and 7. In Gruen zone 7, a statistically significant difference was found for group B (p=0.03). By matching patients for preoperative bone quality and gender, a statistical significant difference was found in proximal bone preservation in favour of ABG-II. In future comparative bone remodelling studies using DEXA, patients should be matched for preoperative bone quality and gender. Résumé Il a été démontré, récemment, que le changement de la pièce fémorale entre l'ABG-1 et l'ABG-2 entraînait une amélioration de la préservation du stock osseux mais ceci n'était pas significatif. En étudiant une série de patients, nous avons souhaité démontrer l'inverse. 24 patients avec une prothèse ABG-2 ont été comparés à différents groupes de patients avec une prothèse ABG-1: (1) 25 patients de notre étude prospective et (2) un groupe de 24 patients sélectionnés, avec une série parfaitement cohérente en termes de sexe, d'âge et de qualité osseuse préopératoire. Les modifications de la densité minérale osseuse (BMD) ont été mesurées à deux ans post opératoires en utilisant la technique DEXA. La préservation du capital osseux est meilleure dans l'ABG-2 que dans l'ABG-1 (y compris dans les deux groupes) au niveau de la partie proximale en zones 1 et 7. Dans la zone 7 de Gruen une différence significative a été trouvée pour le groupe B (p=0.03). Cette étude montre qu'avec une bonne sélection de patients on peut mettre en évidence que la conservation osseuse est meilleure pour l'ABG-2. Dans une étude ultérieure, nous essayerons d'évaluer, selon la technique DEXA le capital osseux en sélectionnant des patients en préopératoire selon la qualité de l'os et le sexe.

Micronuclei (MN) are small, extranuclear bodies that arise in dividing cells from acentric chromosome/chromatid fragments or whole chromosomes/chromatids lagging behind in anaphase and are not included in the daughter nuclei at telophase. The mechanisms of MN formation are well understood; their possible postmitotic fate is less evident. The MN assay allows detection of both aneugens and clastogens, shows simplicity of scoring, is widely applicable in different cell types, is internationally validated, has potential for automation and is predictive for cancer. The cytokinesis-block micronucleus assay (CBMN) allows assessment of nucleoplasmic bridges, nuclear buds, cell division inhibition, necrosis and apoptosis and in combination with FISH using centromeric probes, the mechanistic origin of the MN. Therefore, the CBMN test can be considered as a ''cytome'' assay covering chromosome instability, mitotic dysfunction, cell proliferation and cell death. The toxicological relevance of the MN test is strong: it covers several endpoints, its sensitivity is high, its predictivity for in vivo genotoxicity requires adequate selection of cell lines, its statistical power is increased by the recently available high throughput methodologies, it might become a possible candidate for replacing in vivo testing, it allows good extrapolation for potential limits of exposure or thresholds and it is traceable in experimental in vitro and in vivo systems. Implementation of in vitro MN assays in the test battery for hazard and risk assessment of potential mutagens/carcinogens is therefore fully justified.

Optimization (LO) approaches to production planning. The OPT game was used as the experimental instrument. The subjects were given hint sheets based on MS, TOC/OPT and LO approaches. The results show that production planning by MS and TOC/OPT approaches improve the performance more than the LO approach. Additionally MS was found to improve the performance more than TOC. Statistical power analysis of the data suggests that the laboratory experiment had a high power and the tested approaches had a medium to large effect on performance. © 1997 Elsevier Science Ltd

A simulation study was performed to investigate the statistical power of the revised US Pharmacopeial Convention, Inc. <905> and Bergum's revised test acceptance limits for 95% confidence. In this simulation exercise, relatively small artificial lots of dosage units (20,000 U) were created to represent various probability distributions with increasing levels of defects. A simulation tool was developed to extract valid samples from each lot and perform the compendial test repeatedly for a minimum of 11,000 trials. This paper describes the results of these simulation trials.

Natural radiation is the major source of human exposure to ionising radiation, and its largest contributing component to effective dose arises from inhalation of (222)Rn and its radioactive progeny. However, despite extensive knowledge of radiation risks gained through epidemiologic investigations and mechanistic considerations, the health effects of chronic low-level radiation exposure are still poorly understood. The present paper reviews the possible contribution of studies of populations living in high natural background radiation (HNBR) areas (Guarapari, Brazil; Kerala, India; Ramsar, Iran; Yangjiang, China), including radon-prone areas, to low dose risk estimation. Much of the direct information about risk related to HNBR comes from case-control studies of radon and lung cancer, which provide convincing evidence of an association between long-term protracted radiation exposures in the general population and disease incidence. The success of these studies is mainly due to the c...

The present paper aims at identifying and assessing indicators of the effects of Marine Protected Areas (MPAs) in coral reef regions, based on a bibliography review in ecology, economics and social sciences. First the various effects studied within each of these domains and the variables used to measure them were censused. Potential ecological indicators were assessed through their link with the question used (here termed "relevance") and their "effectiveness" which encompasses the issues of precision, accuracy and statistical power. Relevance and effectiveness were respectively measured by the frequency of use of each indicator and the proportion of significant results in the reviewed articles. For social and economic effects, the approach was not possible due to the low number of references; we thus discussed the issue of finding appropriate indicators for those fields. Results indicate: 1-the unbalance in literature between disciplines; 2-the need for protocols and methodologies which include controls in order to assess MPA effects; 3-an important proportion of ecological indicators with low effectiveness; 4-the large number of ecological effects still not studied or not demonstrated at present. Key words: Marine Protected Areas / Ecological, economic and social indicators / Pluridisciplinary / Coral reef ecosystems / Coastal management Résumé -Quels indicateurs pour évaluer les effets des aires marines protégées sur les écosystèmes coralliens ? Un point de vue pluridisciplinaire. Cet article vise à identifier des indicateurs de l'effet des aires marines protégées (AMP) en milieu corallien, sur la base d'une synthèse bibliographique dans les domaines écologiques, économiques et sociaux, et principalement en milieu corallien. Nous recensons d'abord les différents effets attendus des AMP pour chacun des domaines, et les variables retenues pour les étudier. Les indicateurs écologiques potentiels sont évalués au travers de leur lien avec l'effet étudié (ici appelé « pertinence ») et de leur « efficacité » qui regroupe les notions de précision, justesse et puissance statistique. Pertinence et efficacité sont respectivement mesurées par la fréquence d'utilisation et la proportion de résultats significatifs trouvés dans les articles recensés. Pour les aspects économiques et sociaux, le faible nombre de références ne permet pas une approche comparable à celle utilisée pour les indicateurs écologiques, et nous discutons donc de la question de l'identification d'indicateurs, et suggérons quelques pistes de recherche. Les principales conclusions de ce travail sont : i) le décalage entre les nombres de publications entre disciplines ; ii) la nécessité de protocoles et méthodologies incluant des situations de contrôle pour évaluer les effets des MPA ; iii) la faible efficacité de nombreux indicateurs écologiques ; et iv) le nombre élevé d'effets peu ou pas étudiés ou démontrés à l'heure actuelle. a Corresponding author: dpellet@ifremer.fr 16 D. Pelletier et al.: Aquat. Living Resour. 18, 15-33 (2005)