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PubMedDate not supplied

Issues in the statistical analysis of sperm motion data derived from computer-assisted systems.

Computer-assisted sperm motion measurements present certain features that must be accounted for in statistical analyses. Some are specific to this type of data, whereas others are standard considerations. For example, the measurement of multiple sperm from individuals creates correlations that must be accounted for if each sperm's measurement is used, and unequal variances may arise that need to be addressed if an average measurement from the individual is used. Also, the limitations on the ranges of some measurements create discrepancies between observed and actual means and may make treatment-related effects more difficult to detect--a circumstance that has an impact on study design. When variables that are truly continuous are measured in a discrete fashion, odd effects may arise and care is needed. Other considerations, such as the shapes of distributions and correlations among various measurements, should also be examined. Attention to these details of statistical analysis are vital to proper interpretation of data.

Animals↗
PubMed2003

Adjusting for population heterogeneity: a framework for characterizing statistical information and developing efficient test statistics.

The focus of this work is the TDT-type and family-based test statistics used for adjusting for potential confounding due to population heterogeneity or misspecified allele frequencies. A variety of heuristics have been used to motivate and derive these statistics, and the statistics have been developed for a variety of analytic goals. There appears to be no general theoretical framework, however, that may be used to evaluate competing approaches. Furthermore, there is no framework to guide the development of efficient TDT-type and family-based methods for analytic goals for which methods have not yet been proposed. The purpose of this paper is to present a theoretical framework that serves both to identify the information which is available to methods that are immune to confounding due to population heterogeneity or misspecified allele frequencies, and to inform the construction of efficient unbiased tests in novel settings. The development relies on the existence of a characterization of the null hypothesis in terms of a completely specified conditional distribution of transmitted genotypes. An important observation is that, with such a characterization, when the conditioning event is unobserved or incomplete, there is statistical information that cannot be exploited by any exact conditional test. The main technical result of this work is an approach to computing test statistics for local alternatives that exploit all of the available statistical information.

Data Interpretation, Statistical↗
PubMed1988

The analysis of event history data: a review of progress and outstanding problems.

This paper reviews methods for the analysis of event history data by both parametric (exponential/Poisson) and semi-parametric methods. It identifies a need for software for handling the data structures of complex event histories and shows that, with such software, most Markov and semi-Markov models of event history data may be dealt with in the framework of generalized linear models. Finally, the emergent 'frailty' models for associated risks are discussed together with their implications for statistical software.

Data Interpretation, Statistical↗
PubMed1990

A system of personal computer control programs for tapping experiments.

A system of control and measuring programs on IBM-PC or compatible computers was developed to explore the precision and accuracy of a subject's timing mechanisms in sensorimotor behavior. Various rhythmic patterns composed of several accentuated and non-accentuated tones which the subject has to follow or to reproduce by finger tapping can be designed. All parameters of the stimulus tones, i.e., duration, pitch and inter-tone pause, in a pattern are variable. Two parallel, independent responses can be monitored simultaneously as well. In this way, the mutual influence of responses of two subjects or two responses of one subject can be analyzed. The programs are written in MODULA-2, the output data are in the ASCII format and can be processed by any common statistical package.

Data Interpretation, Statistical↗
PubMed1997

The significance of statistical significance.

Currently, much nursing practice is based on limited evidence, for example, small-scale research, case studies and clinical experience. In a mature science this would be undesirable, but nursing is in the early stages of development as a science, and many of its practices depend on relatively informal knowledge. To encourage the spread of potentially valuable ideas, nurses must be willing to share their clinical experience and journal editors should consider publishing this information. High-quality research is essential to the long-term development of 'evidence-based practice', but it is crucial at the present stage of nursing science that we do not become too concerned with perfect research methodology at the expense of good ideas. This particularly applies to tests of statistical significance. If we accept only information that has demonstrated statistical significance, we risk the dismissal of qualitative research and other information which may be extremely valuable but which have not yet been fully investigated. The aim of this paper is to convince practitioners and journal editors that statistical significance is not the only way to judge clinical importance and to suggest that decisions on what should be submitted and accepted for publication should be based on potential clinical relevance as well as statistical analysis.

Data Interpretation, Statistical↗
PubMed2003

Misuse of standard error of the mean (SEM) when reporting variability of a sample. A critical evaluation of four anaesthesia journals.

BACKGROUND: In biomedical research papers, authors often use descriptive statistics to describe the study sample. The standard deviation (SD) describes the variability between individuals in a sample; the standard error of the mean (SEM) describes the uncertainty of how the sample mean represents the population mean. Authors often, inappropriately, report the SEM when describing the sample. As the SEM is always less than the SD, it misleads the reader into underestimating the variability between individuals within the study sample. METHODS: The aim of this study was to evaluate the frequency of inappropriate use of the SEM in four leading anaesthesia journals in 2001. The journals were searched manually for descriptive statistics reporting either the mean (SD) or the mean (SEM), and inappropriate use of the SEM was noted. RESULTS: In 2001, all four anaesthesia journals published articles that used the SEM incorrectly: Anesthesia & Analgesia 27.7%, British Journal of Anaesthesia 22.6%, Anesthesiology 18.7% and European Journal of Anaesthesiology 11.5%. Laboratory reports and clinical studies were equally affected, except for Anesthesiology where 90% were basic science reports. CONCLUSIONS: One in four articles (n=198/860, 23%) published in four anaesthesia journals in 2001 inappropriately used the SEM in descriptive statistics to describe the variability of the study sample. Anaesthesia journals are encouraged to provide clearer statistical guidelines on how to report data variability in descriptive statistics.

Anesthesiology↗
PubMed1997

Asymmetric dioptric power matrices and corresponding thick lenses.

BACKGROUND: When thickness or separation is taken into account, the dioptric power of systems with obliquely crossed toric surfaces (OCTS), including some corrected and uncorrected human eyes, can be represented by a four-dimensional vector space, provided that an arbitrary 2 x 2 asymmetric matrix is the equivalent power matrix of some optical system. The provision is crucial for the statistical validity of dioptric power matrix methods that take account of thickness. Previous efforts to verify the provision have not been satisfactory. PURPOSE: To verify the provision. METHODS: Prove that an arbitrary 2 x 2 asymmetric matrix is the equivalent power for a thick bitoric lens with obliquely crossed surface. RESULTS: The procedure and new equations needed to find the lens. CONCLUSIONS: The provision holds, which is an important foundation block for the validity of the statistical matrix methods for thick astigmatic systems. The resulting equations also have optical uses other than statistics.

Data Interpretation, Statistical↗
PubMed2002

[Interpretation of visual field with Humphrey Zeiss Analyser].

In the beginning of the article where are defined the notions of the soft of automated perimetry: threshold, kind of tests, the strategy of automated perimetry. Then are shown the steps of automated perimetry interpretation: kind of test and strategy, evaluation of patient reliability, interpretation of the visual field defects (artifacts or no) and statistical analysis.

Data Interpretation, Statistical↗
PubMed2006

[Comments to statistical methods in medical disciplines].

Statistical methods are nowadays one of the main tools for the evidence based medicine. This paper mentions some of the basic ideas necessary for the reader to understand usage of statistical methods.

Data Interpretation, Statistical↗
PubMed1991

Interexaminer reliability for multiple diagnostic test regimens.

A methodology is presented for conducting interexaminer reliability studies when indication for adjustment is based on the outcomes of multiple diagnostic procedures. The adjustment decision-making process is simulated by defining multitest scores to be computed from test battery results and defining threshold values of these scores to demarcate the selection/rejection decision made by the clinician. A probability analysis of random chance agreement suggests that intermediate values of the threshold multitest scores must be used to ensure moderate agreement between observers and the viability of concordance statistics.

Chiropractic↗
PubMed2006

Visual analysis of statistical results from microarray studies of human breast cancer.

Computational and statistical analysis of microarray data is a daunting challenge. Perhaps even more daunting is the biological interpretation of microarray data analysis results. We have previously developed the exploratory visual analysis (EVA) software and database for exploring data analysis results in the context of biological information on each gene available in public databases such as Entrez Gene. EVA brings a flexible combination of statistics and biological annotation to the user's desktop in a straightforward visual interface. Using a publicly available microarray dataset of gene expression response to chemotherapeutic agents in human breast cancer cell lines, we demonstrate the usefulness of the EVA system for interpreting statistical results. EVA can extend previous analyses as well as aid in making novel discoveries. Thus, we anticipate EVA will prove a useful addition to the repertoire of computational methods for microarray data analysis. The EVA software is freely available to academic users.

Antineoplastic Agents↗
PubMed2003

The application of new software tools to quantitative protein profiling via isotope-coded affinity tag (ICAT) and tandem mass spectrometry: II. Evaluation of tandem mass spectrometry methodologies for large-scale protein analysis, and the application of statistical tools for data analysis and interpretation.

Proteomic approaches to biological research that will prove the most useful and productive require robust, sensitive, and reproducible technologies for both the qualitative and quantitative analysis of complex protein mixtures. Here we applied the isotope-coded affinity tag (ICAT) approach to quantitative protein profiling, in this case proteins that copurified with lipid raft plasma membrane domains isolated from control and stimulated Jurkat human T cells. With the ICAT approach, cysteine residues of the two related protein isolates were covalently labeled with isotopically normal and heavy versions of the same reagent, respectively. Following proteolytic cleavage of combined labeled proteins, peptides were fractionated by multidimensional chromatography and subsequently analyzed via automated tandem mass spectrometry. Individual tandem mass spectrometry spectra were searched against a human sequence database, and a variety of recently developed, publicly available software applications were used to sort, filter, analyze, and compare the results of two repetitions of the same experiment. In particular, robust statistical modeling algorithms were used to assign measures of confidence to both peptide sequences and the proteins from which they were likely derived, identified via the database searches. We show that by applying such statistical tools to the identification of T cell lipid raft-associated proteins, we were able to estimate the accuracy of peptide and protein identifications made. These tools also allow for determination of the false positive rate as a function of user-defined data filtering parameters, thus giving the user significant control over and information about the final output of large-scale proteomic experiments. With the ability to assign probabilities to all identifications, the need for manual verification of results is substantially reduced, thus making the rapid evaluation of large proteomic datasets possible. Finally, by repeating the experiment, information relating to the general reproducibility and validity of this approach to large-scale proteomic analyses was also obtained.

Amino Acid Sequence↗
PubMed2005

Partner aggression and problem drinking across the lifespan: how much do they decline?

Cross-sectional analyses from nationally-representative samples demonstrate significant age-related trends in partner aggression and problem drinking. Both behaviors are most prevalent in the early to mid-twenties and increasingly less common thereafter. Aggregate associations based on percentage of individuals displaying the behavior in each age range are dramatically stronger than those found when correlating individuals' ages and behavior. Multilevel modeling demonstrates that group-level effects do not mask associations found at the level of the individual for either problem drinking or partner aggression. An analysis of recent abstracts from psychology journals showed that issues of aggregate and individual data are rarely if ever discussed, and even well-known statistics books in psychology rarely discuss such issues. The interpretation of aggregate data will become increasing important as psychologists themselves, and in collaboration with epidemiologists and sociologists, have access to large data sets that allow for data aggregation. Both aggregate and individual analyses are valid, although they provide answers to different questions. Individual analyses are necessary for predicting individual behavior; aggregate analyses are useful in policy planning for large scale prevention and intervention. Strengths and limitations of cross-sectional community samples and aggregate data are also discussed.

Adolescent↗
PubMedDate not supplied

[The HIV epidemic in the German Federal Republic--infection epidemiology interpretation of numbers of AIDS cases].

Statistical analysis of AIDS case data shows that the flattening out of growth rates of AIDS in the FRG are solely due to the development of case rates in some groups of homosexual men in HIV epicentres and the absence of new infections in haemophiliacs and in patients receiving blood transfusions. Development in the epicentres is interpreted as early saturation. In the other groups that now constitute one-half of the cases reported in 1989 the increase has been steady. Existing gaps in epidemiological infection control are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Estimating hospital deaths due to medical errors: preventability is in the eye of the reviewer.

CONTEXT: Studies using physician implicit review have suggested that the number of deaths due to medical errors in US hospitals is extremely high. However, some have questioned the validity of these estimates. OBJECTIVE: To examine the reliability of reviewer ratings of medical error and the implications of a death described as "preventable by better care" in terms of the probability of immediate and short-term survival if care had been optimal. DESIGN: Retrospective implicit review of medical records from 1995-1996. SETTING AND PARTICIPANTS: Fourteen board-certified, trained internists used a previously tested structured implicit review instrument to conduct 383 reviews of 111 hospital deaths at 7 Department of Veterans Affairs medical centers, oversampling for markers previously found to be associated with high rates of preventable deaths. Patients considered terminally ill who received comfort care only were excluded. MAIN OUTCOME MEASURES: Reviewer estimates of whether deaths could have been prevented by optimal care (rated on a 5-point scale) and of the probability that patients would have lived to discharge or for 3 months or more if care had been optimal (rated from 0%-100%). RESULTS: Similar to previous studies, almost a quarter (22.7%) of active-care patient deaths were rated as at least possibly preventable by optimal care, with 6.0% rated as probably or definitely preventable. Interrater reliability for these ratings was also similar to previous studies (0.34 for 2 reviewers). The reviewers' estimates of the percentage of patients who would have left the hospital alive had optimal care been provided was 6.0% (95% confidence interval [CI], 3.4%-8.6%). However, after considering 3-month prognosis and adjusting for the variability and skewness of reviewers' ratings, clinicians estimated that only 0.5% (95% CI, 0.3%-0.7%) of patients who died would have lived 3 months or more in good cognitive health if care had been optimal, representing roughly 1 patient per 10 000 admissions to the study hospitals. CONCLUSIONS: Medical errors are a major concern regardless of patients' life expectancies, but our study suggests that previous interpretations of medical error statistics are probably misleading. Our data place the estimates of preventable deaths in context, pointing out the limitations of this means of identifying medical errors and assessing their potential implications for patient outcomes.

Bias↗
PubMed1990

Statistical methods in SUPPORT.

The analysis and interpretation of the data collected in SUPPORT provide great potential for understanding the relationships among treatment choices, patient and physician values and preferences, perceptions about the risks and benefits of treatments, institutional characteristics, and outcomes (as measured by quality of life, survival, and satisfaction). The complicated analyses required to elucidate these relationships will pose many technical challenges in dealing with longitudinal observational data collected from seriously ill patients at multiple sites. Major challenges include the handling of incomplete data, proper parameterization of treatment effects, strategies to avoid various potential biases, validating predictive models, and constructing endpoints that combine survival with quality of life. Within the structure of the SUPPORT study, mechanisms have been established to guide the analyses and to ensure their quality and validity.

Confounding Factors, Epidemiologic↗
PubMed2002

[Possibilities of utilising official statistics for health services research].

This report deals with the experiences and problems with using official statistics on a limited area level of Germany's 440 administrative districts. The data comprised health-related issues and were used for an ecological analysis of the determinants of hospital use. We obtained health statistics data from homepages of the German health report, the Federal statistics office, and the 16 statistics offices of the Federal states. We also made use of the data base of the joint regional statistics published by the Federal and regional statistics offices. Finally, there was a co-ordinated inquiry to the regional statistics offices about the supply of data on mortality, hospital discharges, structure of hospital care and several socio-economic indicators. The process of data collecting was mostly unproblematic. On the other hand, not all of the data were available on a limited area level in a satisfying form and quality. For reasons of data protection some information of small districts was transmitted incompletely. Additionally, there are procedural differences between regional statistics offices regarding the differentiation between some variables and in the exchange of data between the federal states. Finally, some problems were due to varying age classifications for different health indicators. For health services research the use of official statistics becomes increasingly comfortable via health reports and Internet. However, for specific questions of research some problems still remain, rising from missing standardised health indicators and deficient availability of limited area health data. Data collection is exacerbated by restrictive interpretation of data protection acts and the different handling of data inquiries in the regional statistics offices. Finally, there is a lack of data on morbidity and use of ambulatory care.

Data Collection↗