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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

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

[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

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

Poisson, compound Poisson and process approximations for testing statistical significance in sequence comparisons.

DNA and protein sequence comparisons are performed by a number of computational algorithms. Most of these algorithms search for the alignment of two sequences that optimizes some alignment score. It is an important problem to assess the statistical significance of a given score. In this paper we use newly developed methods for Poisson approximation to derive estimates of the statistical significance of k-word matches on a diagonal of a sequence comparison. We require at least q of the k letters of the words to match where 0 less than q less than or equal to k. The distribution of the number of matches on a diagonal is approximated as well as the distribution of the order statistics of the sizes of clumps of matches on the diagonal. These methods provide an easily computed approximation of the distribution of the longest exact matching word between sequences. The methods are validated using comparisons of vertebrate and E. coli protein sequences. In addition, we compare two HLA class II transplantation antigens by this method and contrast the results with a dynamic programming approach. Several open problems are outlined in the last section.

Algorithms

Enrichment of oligonucleotide sets with transcription control signals. II: Mammalian DNA.

We studied the frequency distribution of oligonucleotides 10 bp long in a sample of 1.6 Mb of mammalian genes, containing 579 sequences from GenBank(R) 55.0, with the aim of detecting transcription control signals. 2216 decamers had a frequency higher than 10 times the mean and were subjected to further statistical analysis. For each of the 2216 decamers (parents), we counted the individual frequencies of the 30 decamers differing from the parent by one base mutation (progeny) and then calculated two variance/mean chi squares for the progeny, with and without the parent. We then studied the distribution of the ratio between the two chi squares. Out of 2216 decamers, 346 had a chi square ratio of 1.9 or larger. In this final set, which corresponds to less than 0.033 per cent of all possible decamers, 18 were found to contain 23 eukaryotic transcription control elements 5-10 bp of length, such as Sp1 and others. Furthermore, when compared to 210 random sets containing 346 decamers, this set contains a highly significant excess of the longer signals.

Algorithms

Statistical issues arising from mouse micronucleus assay experiments of Ashby and co-workers.

Data from a series of mouse micronucleus assays have been reanalysed to illustrate various statistical issues raised by Ashby and co-workers during the development of the assay. Most of the statistical points discussed in these earlier papers can be explained by the stochastic nature of the data. Reanalysis shows that the type of data collected in mammalian micronucleus assays is amenable to analysis by standard biometric methods. It is concluded that statistical analysis has an important role in the exploration and interpretation of data from the micronucleus assay.

Analysis of Variance

Dealing with large data sets.

Collection, storage and retrieval of large amounts of data from multiple experiments for subsequent reduction, graphing and statistical analysis need not be a burdensome task. Although turnkey systems may offer significant economies for single well-defined and repetitive tasks, they may not permit sufficient flexibility to achieve the diverse aims required by many research programs. Using popular microcomputers to run one or a few experimental subjects may confront the investigator not only with significant bookkeeping problems, but also with an allocation of labor resources to computer maintenance and support that might be better invested in research effort. By using networked minicomputers, economies of scale emerge both in data collection, transfer, reduction, and analysis, as well as in maintenance, support, and scientific effort.

Data Collection