Statistical considerations for performing multiple tests in a single experiment. 3. Repeated measures over time.
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The effect of order has been previously addressed in test-retest studies but its effect on the presentation of more than one test, in the same time, is often underestimated. This study has shown that when two rating scales were given sequentially, each scored lower if received second in the pair, and that this particular form of order effect (occasion effect) was enough to affect markedly agreement on caseness when utilizing standard cut-off scores. It is therefore important that research workers not only adopt design strategies such as counterbalanced presentation, but also analyse their data for the effects of test order and position within such designs.
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In 47 atopic subjects, skin-prick testing to 10 common allergens was performed, and specific IgE to the same allergens was assessed by the multi-allergosorbent chemiluminescent assay (MAST-CLA). Overall agreement between the tests was 66.4% for conventionally positive skin tests (weal diameter greater than or equal to 3 mm), rising to 78.5% when a positive skin test was defined as having a weal diameter greater than or equal to 5 mm. Agreement between the tests was statistically significant for all allergens except Alternaria. A history was obtained from each subject of the presence or absence of allergic symptoms on exposure to cats, and whether there was a history of grass pollen allergy. MAST-CLA testing for specific IgE to cat dander predicted a history of cat allergy with an efficiency of 74.5%, while a positive MAST-CLA test for Cocksfoot grass predicted a history of grass pollen allergy with an efficiency of 85.1%. Similar results were obtained on skin testing for these allergens. We conclude that MAST-CLA gave results comparable to those obtained by skin-prick testing, and correlated equally well with the history of allergic symptoms.
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Eight groups of rhesus monkeys totaling over 1,000 animals were captured in the virgin trapping grounds of Jammu and Kashmir, India. Individual caging and special handling technics were utilized to prevent cross-contamination during capture, holding, and subsequent shipment to quarantine facilities in the United States. Immediately following the arrival of the monkeys, 5 consecutive blood samples were obtained at approximately 2-wk intervals, and the sera were rested for neutralizing antibody against Herpesvirus simiae. In order to assure the greatest sensitivity possible, sera were not heat-inactivated and were tested against only 10 TCID50 units of virus in addition to the more commonly used concentration of 100 TCID50 units. The first test detected 80-90% of the positive animals within each group, and only 1 seroconversion was noted after the second test. Seventy-three percent of the adults, 36.6% of the young adults, and 12.4% of the juvenile macaques were found to be antibody-positive. Considering the measures employed to prevent cross contamination, these percentages probably reflect the true prevalence of B virus infection in these rhesus monkeys at the time of their capture in the wild.
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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.
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.
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.
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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.
This report gives an account of the patterns of requesting of multiple biochemical tests in a large general hospital and the frequency of abnormal test results in different hospital departments. There are appreciable differences between some areas in the frequency of requests for multiple testing and in the proportions of abnormal results. If it is assumed that clinicians should be aware of abnormal values and their progress, facilities for multiple testing are desirable and economically justifiable.
The Multiple Sleep Latency Test (MSLT) has gradually gained acceptance as an objective equivalent of the complaint of sleepiness. The history of this test and questions considering the validity of the MSLT in different situations are discussed.