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PubMed1996

Multiple test procedures for dose finding.

The problem of identifying the lowest dose level for which the mean response differs from that at the zero dose level is considered. A general framework for stepwise testing procedures that use contrasts among the dose level means is proposed. Using this framework, several new procedures are derived. These and some existing procedures, including that of Williams (1971, Biometrics 27, 103-117; 1972, Biometrics 28, 519-531), are compared analytically and by an extensive simulation study for the normal theory balanced one-way layout case. It is pointed out that the procedures based on the so-called step and basin contrasts proposed by Ruberg (1989, Journal of American Statistical Association 84, 816-822) have excessively high type I familywise error rates (FWEs) and, hence, they should not be used. Some findings of the simulation study are as follows: For monotone dose mean configurations, Williams' procedure and two step-down test procedures based on Helmert and linear contrasts offer the best performance. For nonmonotone dose mean configurations, the performance of Williams' procedure does degrade somewhat, but the other two procedures are still the best. For more complex designs, a simple step-down test procedure that uses any alpha-level tests (not necessarily t-tests) to compare each dose level with the zero dose level controls the FWE and is the only alternative available, but its power is rather low, especially under nonmonotone configurations. Step-up procedures are generally dominated by step-down procedures when the same contrasts are used although the differences are not great.

Animals↗
PubMed1992

Maintenance of wakefulness test and multiple sleep latency test. Measurement of different abilities in patients with sleep disorders.

The multiple sleep latency test and the maintenance of wakefulness test were administered on the same day to 258 consecutive patients whose clinical presentation required evaluation for excessive sleepiness. While the MSLT is the standard test for assessing excessive daytime sleepiness, the MWT may have some clinical advantage over the MSLT when the assessment of daytime alertness is the primary goal. To explore further the relationship between alertness and sleepiness, we have conducted a thorough analysis of the similarities, differences, and correlations between MWT and MSLT. The results of this study show that the coefficient of correlation between MSLT and MWT (r = 0.41), although statistically significant, accounts for less than 17 percent of the variability between the two tests. Factor analysis suggests that two factors, alertness and sleepiness, account for 91 percent of all variance. Our data demonstrate that patients with diagnosable disorders of excessive somnolence may be discordant on the two tests (eg, having low sleep latency on MSLT but high sleep latency on MWT). Specifically, we found that some patients with abnormally low MSLT scores were able to stay awake when asked to do so on the MWT, and conversely, some patients who failed to stay awake when asked to do so on the MWT were unable to fall asleep quickly on the MSLT. We conclude that the MWT and MSLT measure different abilities and that the MWT may be a useful adjuvant daytime test in many clinical situations.

Adult↗
PubMedDate not supplied

[Method for calculating the distribution of randomly expected scores in a false-true-do not know-type of test].

Multiple choice tests have been used widely in the evaluation of knowledge. The lowest passing limit is generally chosen arbitrarily. Better and more objective criteria may arise from analyzing the distribution of correct and incorrect answers as expected by chance. In order to calculate the distribution of correct answers and the difference between correct and incorrect answers (core) we propose the use of a method based on a gaussian distribution. The distribution of scores expected by chance is approximated by a gaussian distribution with a mean of zero and a standard deviation SD = square root of n(pA + pE), and the distribution of the total number of correct answers has a mean of npA and SD = square root of npApE, where n is the total number of questions, and pA and pE are the probabilities of having a correct and an incorrect answer, respectively. The formulae are applicable to questions type false/true/do not know and to the more common type of one correct in five options. Once the chance distribution is known, it can be compared with the distribution of scores or correct answers obtained, which can then be used to separate people in two groups: those that answer the test as expected or worse than expected by chance, and those that answer the test better than expected by chance. The first group should not be passed. The passing of individuals in the second group can be decided by additional criteria.

Educational Measurement↗
PubMed1992

Writing a multiple-choice test question.

Multiple-choice test questions are the most widely used and highly regarded of the presently available objective or selective test items. They can be used to test all levels of learning and are applicable to the measurement of most important educational outcomes. Although it is difficult to construct these questions well, they are versatile and can be used in settings involving large numbers of students.

Education, Medical, Graduate↗
PubMed1984

Peritz' F test: basic program of a robust multiple comparison test for statistical analysis of all differences among group means.

Peritz' F test has previously been found to be the most robust statistical multiple comparison test able to hold all comparisons among group means to a given experimentwise error rate. A BASIC program which will perform this test quickly on a desk-top microcomputer, needing fewer than 11 kbytes of RAM memory, is presented. The program is run in the author's laboratory using an inexpensive VIC-20 computer.

Computers↗
PubMed1983

HLA-DR3 associated genetic control of response to multiple skin tests with new tuberculins.

Multiple skin testing with mycobacterial antigenic preparations reveals distinct reaction patterns, which might be relevant to the development of mycobacterial disease in man. Previous work has shown that HLA-DR associated factors correlate with the position of a leprosy patient in the immunopathological spectrum of leprosy. This study was undertaken to see whether these skin test patterns in healthy persons do show any association with HLA-DR types. Out of a group of 74 healthy Caucasoid individuals HLA-DR3 was observed to be absent from the 16 individuals who did not respond to any of the mycobacterial antigens tested. This is a striking difference from the distribution of HLA-DR3 both among the 17 individuals who responded to all mycobacterial antigens tested (P = 0.005) and the 41 individuals who responded to some but not all antigens (P = 0.015). These data show that an HLA-DR3 associated genetic factor controls, albeit indirectly, skin test responsiveness to mycobacterial antigens. It may be significant that this same HLA-DR determinant is implicated in deciding the type of disease to be developed by a leprosy patient.

Genes, MHC Class II↗
PubMed1986

Changes in non-specific immune responses induced by repeated delayed-type hypersensitivity skin testing with multiple antigens.

Delayed-type hypersensitivity (DTH) responses following in vivo multiple-antigen skin testing in healthy individuals have been well described as indicators of immune responsiveness. In contrast, little information is available about how repeated in vivo multiple antigen skin testing could effect major non-specific parameters of immune responses. In a prospective study of 22 healthy adult volunteers, DTH skin tests were performed 6 times at 4-week intervals over a 28-week course. Prior to each skin test, blood specimens were collected and evaluated by in vitro assays of non-specific parameters related to humoral and cell-mediated immune (CMI) responses. Sustained effects of repeated skin tests in the volunteers included decreased numbers of circulating polymorphonuclear leukocytes (PMNLs), increased serum IgM levels and decreased DTH responses in those individuals originally designated as high DTH responders. Increased lymphocyte transformation with PHA was transiently observed in the study group at 4-12 weeks into the study. In contrast, numbers of T, B and total lymphocytes, levels of IgG, IgA, and circulating immune complexes, and serum blocking activity did not change. This study suggests that few alterations in non-specific immune parameters may be expected to occur in normal, adult individuals as a result of repeated multiple-antigen skin tests.

Adolescent↗
PubMed1995

Chromosomal instability in multiple endocrine neoplasia type 1. Cytogenetic evaluation with DEB test.

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant condition with high penetrance and variable expressivity, in which tumors or hyperplasia occur in two or more endocrine organs. Some authors have investigated chromosomal instability in MEN 1 and MEN 2; the results are controversial. Chromosome analyses were performed on lymphocytes from seven patients with MEN 1, four healthy first-degree relatives (three of whom were children), six phenotypically normal volunteers, and three patients with Fanconi's anemia. To evaluate chromosomal instability we analyzed phytohemagglutinin-stimulated lymphocyte cultures with and without diepoxibutane. We observed an increase in the frequency of spontaneous chromosomal alterations in four patients. After the DEB test we found an increase in chromatid breakages, gaps, and exchange figures. These findings support the inclusion of the MEN 1 syndrome among the disorders with "chromosomal instability."

Adult↗
PubMed1978

[Application of the multiple vocabulary test to assessing mental disorders].

The multiple vocabulary test has been used to investigate approaches to objectifying general mental deterioration. Compared to methods used to determine the actual level of intelligence, the premorbid levels of intelligence which were determined with the use of the multiple vocabulary test were roughly the same for patients with brain injuries that cannot be detected by means of specialized instruments. In the case of patients where brain injuries were detectable through the use of instruments, the premorbid level of intelligence was significantly higher than the actual intelligence level. Patients with general mental deterioration showed highly significant differences between premorbid and actual levels of intelligence. The results obtained indicate that the multiple vocabulary test is a useful means of diagnosing general mental deterioration due to organic or psychological factors. Also discussed by the authors in their present paper are hitherto unsolved problems that stand in the way of an objective diagnosis of dementia and loss of intelligence.

Humans↗
PubMed1983

Multimodality evoked potentials and neurophysiological tests in multiple sclerosis. Effects of hyperthermia on test results.

Data on critical frequency of photic driving (CFPD), frequency following response (FFR), and visual, somatosensory (peroneal nerve), and brain-stem auditory evoked potentials (EPs) were obtained from 20 patients who had clinically definite multiple sclerosis and ten healthy normal subjects in a controlled, balanced study under normothermic and hyperthermic (+1 degrees C) conditions with a test-retest interval of one week. Normal subjects' test results showed no changes during hyperthermia. Patients' EP and CFPD data correlated well with history, clinical signs, and symptoms during both normothermia and hyperthermia. The FFR test data were equivocal and not fully analyzed. Data from the four other tests showed additional patient abnormalities during hyperthermia. Multimodality testing increased the number of patient abnormalities compared with single tests, and the number increased further during hyperthermia. Test-retest reproducibility was higher during hyperthermia.

Adult↗
PubMed1997

The latent class model for multiple binary screening tests.

Given multiple binary tests, such as repeated application of a blind screening test to each individual in a sample, we attempt to estimate the prevalence, sensitivity and specificity of the test without knowing the true disease status of those tested (gold standard). This problem is equivalent to finding the mixing distribution of a mixture of binomial distributions. We suggest a new method to determine the number of latent classes. Our simulations show that the coverage probabilities of the bootstrap confidence intervals of our estimates are correct. Our methods are illustrated by examples from published medical research.

Algorithms↗