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PubMedDate not supplied

Comparison of visual inspection and statistical analysis of single-subject data in rehabilitation research.

Single-subject designs are being advocated to conduct outcome research in rehabilitation environments. The methods provide an alternative to traditional designs based on statistical comparisons across groups. Data analysis in single subject research does not rely on statistical hypothesis testing of responses collected from a sample of subjects. Instead, visual inspection of patient responses graphed over time is the usual method of data analysis in single-subject research. This study examined the agreement between visual analysis and statistical tests of single-subject data for 42 hypothetical single-subject graphs. Specially constructed graphs allowed the systematic manipulation of different treatment effect sizes across a commonly used single-subject design. Thirty-two rehabilitation and health care providers rated each of the 42 graphs to determine whether a clinically significant treatment effect existed across the phases of the designs. Data analysis focused on two questions: (1) How much agreement was there between visual judgments and the results of statistical tests? and (2) What level of treatment effect was required to produce a finding of visual versus statistical significance? The agreement between visual analysis and statistical significance was high (86%). The sensitivity of visual inferences compared with statistical test results was 0.84, specificity was 0.88, and positive predictive value was 0.91. Both visual and statistical procedures were sensitive to medium and large treatment effects in the 42 single-subject graphs examined in this study.

Audiovisual Aids↗
PubMed2003

Statistical sampling and hypothesis testing in orthopaedic research.

The purpose of the current article was to review the process of hypothesis testing and statistical sampling and empower readers to critically appraise the literature. When the p value of a study lies above the alpha threshold, the results are said to be not statistically significant. It is possible, however, that real differences do exist, but the study was insufficiently powerful to detect them. In that case, the conclusion that two groups are equivalent is wrong. The probability of this mistake, the Type II error, is given by the beta statistic. The complement of beta, or 1-beta, representing the chance of avoiding a Type II error, is termed the statistical power of the study. We previously examined the statistical power and sample size in all of the studies published in 1997 in the American and British volumes of the Journal of Bone and Joint Surgery, and in Clinical Orthopaedics and Related Research. In the journals examined, only 3% of studies had adequate statistical power to detect a small effect size in this sample. In addition, a study examining only randomized control trials in these journals showed that none of 25 randomized control trials had adequate statistical power to detect a small effect size. However, beta, or power, is less well understood. Because of this, researchers and readers should be aware of the need to address issues of statistical power before a study begins and be cautious of studies that conclude that no difference exists between groups.

Epidemiologic Research Design↗
PubMed1985

The statistical content of published medical research: some implications for biomedical education.

Medical students and doctors need training in biostatistics. The use of analytic statistics in a leading general medical journal is reported. Of 760 consecutive research and review articles, 42% use statistical methods beyond elementary descriptive statistics. Critical reading of the medical literature requires an understanding of many statistical methods. The frequency of use of such methods may help identify those which should receive greater attention in instructional programmes within the medical curriculum. Based on the frequencies and our understanding of the importance of broad statistical concepts, recommendations are developed for the basic course in biostatistics. The integration of several more advanced statistics modules into clinical training is also suggested. The use is recommended of clinically oriented textbooks in biostatistics and current journal articles to help make instruction in statistics more relevant for preclinical students, and to help clinicians appreciate the applications of statistics to their work.

Biometry↗
PubMed2003

Randomized clinical trial: myths around elementary statistical principles.

In discussing design and results of randomized clinical trials, in particular with clinical oncologists, one often encounters the opinion that a phase III trial is a complicated, highly costly, and difficult task. Part of this opinion seems to originate in myths around underlying biostatistical principles such as randomization, sampling and sample size, statistical hypotheses, statistical error probabilities, and statistical power. This work clarifies basic statistical issues of randomized clinical trials and the interpretation of their results. Six issues ('myths') relevant for the design of clinical trials and the interpretation of their results are addressed. They concern choice of study design, choice of participating centers, and recruitment of patients as well as statistical questions of establishing study hypotheses and interpreting p values. These myths are shown to be caused primarily through a misunderstanding of statistical inference and statistical thinking that can be avoided when a rational understanding of statistical principles is translated into a clinical research approach. We also conclude that before clinical evidence is summarized from different studies each study should be examined thoroughly.

Bias↗
PubMed1981

Six statistical suggestions for surgeons.

Statistical analysis has become very important in medical research. The large number and variety of statistical techniques required to appropriately handle different types of medical research make it impossible for most physicians to acquire enough statistical expertise to analyze critically the details of many reports. However, a basic understanding of certain fundamental principles of statistical analysis is vital if statistical errors and misapplications are to be identified and prevented. The basic principles underlying six common statistical errors are discussed and a guide to pertinent literature is provided so that the practicing physician without special statistical knowledge can be in a better position to understand and interpret statistical analysis in the medical literature.

General Surgery↗
PubMed1979

Statistics in Japanese universities.

The teaching of statistics in the U.S. and Japanese universities is briefly reviewed. It is found that H. Hotelling's articles and subsequent relevant publications on the teaching of statistics have contributed to a considerable extent to the establishment of excellent departments of statistics in U.S. universities and colleges. Today the U.S. may be proud of many well-staffed and well-organized departments of theoretical and applied statistics with excellent undergraduate and graduate programs. On the contrary, no Japanese universities have an independent department of statistics at present, and the teaching of statistics has been spread among a heterogeneous group of departments of application. This was mainly due to the Japanese government regulation concerning the establishment of a university. However, it has recently been revised so that an independent department of statistics may be started in a Japanese university with undergraduate and graduate programs. It is hoped that discussions will be started among those concerned on the question of organization of the teaching of statistics in Japanese universities as soon as possible.

History, 20th Century↗
PubMed1999

On two methods of statistical image analysis.

The computerized brain atlas (CBA) and statistical parametric mapping (SPM) are two procedures for voxel-based statistical evaluation of PET activation studies. Each includes spatial standardization of image volumes, computation of a statistic, and evaluation of its significance. In addition, smoothing and correcting for differences of global means are commonly performed in SPM before statistical analysis. We report a comparison of methods in an analysis of regional cerebral blood flow (rCBF) in 10 human volunteers and 10 simulated activations. For the human studies, CBA or linear SPM standarization methods were followed by smoothing and computation of a statistic with the paired t-test of CBA or general linear model of SPM. No standardization, linear, and nonlinear SPM standardization were applied to the simulations. Significance of the statistic was evaluated using the cluster-size method common to SPM and CBA. SPM employs the theory of Gaussian random fields to estimate the cluster size distributions; simulations described in the Appendix provided empirical distributions derived from t-maps. The quantities evaluated were number and size of functional regions (FRs), maximum statistic, average resting rCBF, and percentage change. For the simulations, the efficiency of signal detection and rate of false positives could be evaluated as well as the distributions of statistics and cluster size in the absence of signal. The similarity of the results yielded by similar methods of analysis for the human studies and the simulated activations substantiates the robustness of the methods for selecting functional regions. However, the analysis of simulated activations demonstrated that quantitative evaluation of significance of a functional region encounters important obstacles at every stage of the analysis.

Adult↗
PubMed2001

Nonlinear and extra-classical receptive field properties and the statistics of natural scenes.

The neural mechanisms of early vision can be explained in terms of an information-theoretic optimization of the neural processing with respect to the statistical properties of the natural environment. Recent applications of this approach have been successful in the prediction of the linear filtering properties of ganglion cells and simple cells, but the relations between the environmental statistics and cortical nonlinearities, like those of end-stopped or complex cells, are not yet fully understood. Here we present extensions of our previous investigations of the exploitation of higher-order statistics by nonlinear neurons. We use multivariate wavelet statistics to demonstrate that a strictly linear processing would inevitably leave substantial statistical dependencies between the outputs of the units. We then consider how the basic nonlinearities of cortical neurons--gain control and ON/OFF half-wave rectification--can exploit these higher-order statistical dependencies. We first show that gain control provides an adaptation to the polar separability of the multivariate probability density function (PDF), and, together with an output nonlinearity, enables an overcomplete sparse coding. We then consider how the remaining higher-order dependencies between different units can be exploited by a combination of basic ON/OFF point nonlinearities and subsequent weighted linear combinations. We consider two statistical optimization schemes for the computation of the optimal weights: principal component analysis (PCA) and independent component analysis (ICA). Since the intermediate nonlinearities transform some of the higher-order dependencies into second-order dependencies even the basic PCA approach is able to exploit part of the redundancies. ICA ignores this second-order structure, but can exploit higher-order dependencies. Both schemes yield a variety of nonlinear units which comprise the typical nonlinear processing properties, such as end-stopping, side-stopping, complex-cell properties and extra-classical receptive field properties, but the 'ideal' complex cells seem only to occur with PCA. Thus, a combination of ON/OFF nonlinearities with an integrated PCA-ICA strategy seems necessary to exploit the statistical properties of natural images.

Algorithms↗
PubMed2004

[A review of statistical analysis methods in measurement data].

Measurement data, which is obtained by measuring the size of numeric value, is consisted of numerical variables. In clinic research, the collected data covers quite of numerical variables. Composed of those numerical variables, the measurement data has to be correspondingly analyzed in the special statistical methods in the light of their design methods. The statistical methods of measurement data include descriptive statistics and inferential statistics. Descriptive statistics is mainly used to describe the distribution laws and the characters/features of the data. For instance, when measuring the central tendency and dispersion tendency of the data, methods such as calculating the mean and the standard deviation can be considered. Inferential statistics is mainly employed to estimate the confidence limit such as estimating the 95% confidence interval and to have the hypothesis testing in the example of having t test and analysis of variance. By highlighting the specific statistical methods of measurement data, this review intends to help the clinicians and researchers select correct statistical methods in accordance with measurement data.

Data Interpretation, Statistical↗
PubMed2005

[Statistical quality requires improvement in ophthalmic research].

The improper use of statistical analysis method and inadequate quality of experimental design are common in ophthalmic research. These problems originated from ignoring the importance of statistics or have a bias against the statistics by the researcher. Therefore, the misunderstanding of statistics must be cleared up, it is important for the researcher to familiar with statistical knowledge, instead of simply relying on the cooperation with statistics specialists. Researcher should devote much attention to the study of statistics and enhance the ability to apply it in practice. Statistics is not only one of the supports of evidence-based medicine, but it is also very important in keeping sustainable scientific development of science.

Ophthalmology↗
PubMed1986

Research design and statistical procedures used in the Journal of Family Practice.

To determine whether articles published in The Journal of Family Practice contain statistical content that is easily understood by the general reader, all original articles published during a two-year period were reviewed to determine the frequency of use of different research designs and statistical procedures. Eighty-eight percent of the articles used the cross-sectional design. No statistical methods were reported in 46 percent of the articles; 13 percent reported descriptive statistics only. The chi-square statistic and t test were the most commonly used statistical procedures. Readers of The Journal of Family Practice, therefore, needed only an elementary knowledge of statistics to understand the statistical content of three quarters of the original articles.

Cross-Sectional Studies↗
PubMed1985

Statistical methods in anesthesia articles: an evaluation of two American journals during two six-month periods.

Simple criteria were used to evaluate the statistical analyses in 243 articles from two American anesthesia journals published in the latter six months of 1981 and 1983. Eighty-two percent of the articles reported the use of control measures and 37% reported randomization of treatment, where they were possible. Data were classified as nominal, ordinal, or interval; as independent or related samples; as two-sample or more-than-two-sample cases. The descriptive, inferential, and correlative tests used were evaluated for appropriate application and primary errors were identified. Nine percent of the 722 descriptive statistics had major errors, most of which were a description of ordinal data as though they were interval. The incidence of erroneous applications of 394 inferential statistical tests was 78%. Nearly three-quarters of the 308 primary inferential statistical errors involved either use of a test for independent samples on related data (and vice versa) or multiple applications of an uncorrected test to the same data. Only 4% of the 113 statistics of association were considered erroneous, most because the method was not identified. No differences were detected in the incidence of errors in either experimental design or statistical analysis across time or across the two anesthesia journals. Fifteen percent of the 243 articles in both journals at both times were without major errors in statistical analysis. Recognition of potential sources of error should make it easier for investigators to use experimental designs and statistical analyses appropriate to their needs.

Anesthesia↗
PubMed1996

[Statistics in the clinical research on drugs. A study of original articles emanating from Spanish centers].

BACKGROUND: The aim of this study was to evaluate statistical analysis reported in clinical investigation articles of Spanish drugs. METHODS: Original articles provided by Spanish centers and indexed in EMBASE in 1975, 1980, 1985 and 1990 were studied. The type of statistics used, their description and different aspects of results presentation are reported. RESULTS: Two hundred eighty-eight articles were studied of which 73.3% used inferential statistics with 57.3% presenting an adequate description of the same. The most frequently used statistical tests were bivariant techniques, mainly the Student's t test (33.7%) and chi square test (28.8%). The complexity of the statistical tests increased progressively in the years reviewed being greater in the articles published in foreign journals. The results were presented adequately and in a comprehensive form in 40% of the cases. Confidence intervals were used in 22.2% in the presentation of the results. In 49.1% of the articles statistical significance favored the group receiving the therapy studied. Of the 46.6% which did not present differences only 9.3% the statistical power was calculated. CONCLUSIONS: Although an improvement was observed in the years evaluated, the articles on clinical drug investigation carried out in Spanish centers still present insufficient information on statistical methodology, particularly in those published in Spanish journals.

Clinical Trials as Topic↗
PubMed1998

[Statistical models with reference to their value for medical process quality assurance].

Since the revision of the KVG (Art. 58) (Health Insurance Law) in 1995, systematic scientific monitoring is laid down by statute in order to ensure quality (Health Insurance Regulations; KVV Art. 77). In addition, the statistics law of 1992 prescribes the BFS statistics (with ICD coding) (model 1). Since 1983 the "Arbeitsgemeinschaft Schweizerischer Frauenkliniken" (ASF) (The Swiss Working Group of Obstetrical and Gynecological Institutions) has been maintaining a common set of statistics which amongst other things also serves for quality assurance purposes (model 2). In 1995 a number of surgical hospitals joined together under the title "Arbeitsgemeinschaft für Qualitätssicherung in der Chirurgie" (AQC) (Swiss Surgical Quality Assurance Working Group) and now also maintain similar common statistics (model 3). In this paper the three above-mentioned models are described with regard to their suitability for process quality assurance. Whilst the BFS statistics are unsuitable for this purpose, the two other methods of data collection largely fulfil the requirements for process quality assurance by using statistical models. The largest deficiency in the ASF and AQC statistics is the lack of comprehensive geographical coverage which in contrast is provided by the BFS statistics thanks to statutory requirements. However, all three models are unsuitable for the areas of structure and outcome quality assurance. Therefore other solutions must be sought for these purposes.

Data Collection↗
PubMed2002

Iterative versus filtered backprojection reconstruction for statistical parametric mapping of PET activation measurements: a comparative case study.

The significance of task-induced cerebral blood flow responses, assessed using statistical parametric mapping, depends, among other things, on the signal-to-noise ratio (SNR) of these responses. Generally, positron emission tomography sinograms of H(2)(15)O activation studies are reconstructed using filtered backprojection (FBP). Alternatively, the acquired data can be reconstructed using an iterative reconstruction procedure. It has been demonstrated that the application of iterative reconstruction methods improves image SNR as compared with FBP. The aim of this study was to compare FBP with iterative reconstruction, to assess the statistical power of H(2)(15)O-PET activation studies using statistical parametric mapping. For this case study, PET data originating from a bimanual motor task were reconstructed using both FBP and maximum likelihood expectation maximization (ML-EM), an iterative algorithm. Both resulting data sets were statistically analyzed using statistical parametric mapping. It was found, with this dataset, that the statistical analysis of the iteratively reconstructed data confirm the a priori expected physiological response. In addition, increased Z scores were obtained in the iteratively reconstructed data. In particular, for the expected task-related response, activation of the posterior border of the left angular gyrus, the Z score increased from 3.00 to 3.96. Furthermore, the number of statistically significant clusters doubled while their volume increased by more than 50%. In conclusion, iterative reconstruction has the potential to increase the statistical power in H(2)(15)O-PET activation studies as compared with FBP reconstruction.

Brain Mapping↗
PubMed1981

[Medical statistics in compulsory accident insurance].

The medical statistics in the compulsory accident insurance are conceived as a secondary statistic. It includes both injuries and medical services. Since the Swiss National Accident Insurance Fund started in 1918, there were regular reports about medical statistics. The current statistics of the agency are organized as a sampling statistic. Only disability benefits are covered in toto. The statistical organization permits the identification of single cases in terms of specific characteristics and to analyze them further. The new accident insurance law makes accident insurance obligatory for all persons who are not self-employed. The regulation, included in this law, to record statistics uniformly will hopefully help toward the improvement of medical statistics within the compulsory accident insurance scheme.

Accidents↗
PubMed1989

Screening for possible human carcinogens and mutagens. False positives, false negatives: statistical implications.

A screening method aimed at identifying potential human carcinogens using either animal cancer bioassays or short-term genotoxic assays has 4 possible results: true positive, true negative, false positive and false negative. Such a categorisation is superficially similar to the results of hypothesis testing in a statistical analysis. In this latter case the false positive rate is determined by the significance level of the test and the false negative rate by the statistical power of the test. Although the two types of categorisation appear somewhat similar, different statistical issues are involved in their interpretation. Statistical methods appropriate for the analysis of the results of a series of assays include the use of Bayes' theorem and multivariate methods such as clustering techniques for the selection of batteries of short-term test capable of a better prediction of potential carcinogens. The conclusions drawn from such studies are dependent upon the estimates of values of sensitivity and specificity used, the choice of statistical method and the nature of the data set. The statistical issues resulting from the analysis of specific genotoxicity experiments involve the choice of suitable experimental designs and appropriate analyses together with the relationship of statistical significance to biological importance. The purpose of statistical analysis should increasingly be to estimate and explore effects rather than for formal hypothesis testing.

Bayes Theorem↗
PubMed2002

Fatal alcohol poisoning: medico-legal practices and mortality statistics.

Compilation of mortality statistics from death certificate data is based on international and national conventions which in certain situations result in the underlying cause-of-death other than that established and reported by the physician. The present study compares all fatal alcohol poisonings in 1997 as registered on forensic toxicological grounds at the accredited central laboratory and as presented in the national cause-of-death statistics, according to the underlying cause-of-death, by applying international statistical rules and principles in ICD-10. Four groups were formed, and case frequencies in each group were obtained from forensic toxicological data, group "T51" for acute poisonings due to alcohol alone, and group "Comb" for acute alcohol poisonings combined with some drug, medicament or other biological substance, and from cause-of-death statistics data, group "X45", for deaths from alcohol poisoning, and group "F102" for those medico-legal fatal alcohol poisoning deaths which at the statistics office were inferred to be due to alcoholism. The study shows that in Finland the officially compiled statistics on fatal alcohol poisonings, when compared with medico-legal statements based on forensic toxicological examinations, were underrepresented by 31.4% in 1997. About two-thirds of this underrepresentation is explained by preferring, as the underlying cause-of-death, alcoholism to acute alcohol poisoning, and about one-third by preferring, in cases of acute combined poisonings, the drug component to the alcohol. From 1998 onwards, more emphasis has been put on the alcohol component when coding medico-legally proven accidental deaths from simultaneous poisoning with alcohol and a medicinal agent. This change in coding practices presumably explains the subsequent decline in the annual underrepresentation rate of alcohol poisoning in mortality statistics to the level of 15-16%. It is concluded that the present ICD rules inevitably lead to underrepresentation of alcohol poisonings in the mortality statistics, and conceptual and practical proposals for future procedures are made.

2-Propanol↗