No Evidence for Relationship between Biorhythms and Industrial Accidents

According to the popular biorhythm model accidents are more likely to occur during the “critical days” of three sine wave-like cycles that display periodicities of 23 days, 28 days, and 33 days. Analyses of 400 mining accidents from two separate industries demonstrated that the number of employees who were involved with accidents on their individual critical days of the different cycles did not differ significantly from chance expectancy. Furthermore the number of employees involved in accidents when their cycles were in ascending phases (presumably associated with positive behaviors) did not differ significantly from the number of employees who were involved in accidents when their cycles were in the descending phases, presumably associated with negative behaviors. We have found neither empirical nor theoretical support for the biorhythm model.

Double-blind procedure: an assessment in a study of lithium prophylaxis

SynopsisFifty-seven patients with primary affective disorder who were in a double-blind outpatient study to evaluate the prophylaxis of lithium were questioned as to whether they believed they were receiving lithium or placebo. Research nurses who were ‘blind’ to the patients' medication and a close relative living with each patient were also questioned. Nearly all patients (96%) said they believed they were receiving lithium, ascribing this belief in 63% of the cases to a perceived improvement in condition. In only 14% of the cases on lithium was the presence of side-effects implicated in the patients' beliefs. One of the three nurses had a correct guess rate in excess of chance expectancy. All nurses tended to be more accurate in their guesses in the cases of patients who had been in prophylactic trials of over 15 months' duration than for patients with briefer periods in the study. Patients' relatives were, as a group, extremely accurate, their correct guess rate exceeding chance expectancy at the 0·001 level.

Uncertain Responses on Multiple-Choice Examinations

100 students were asked to label item responses on two multiple-choice tests as sure, uncertain, and guess. The uncertain category was significantly different from the sure and guessed response categories, and from the theoretical chance expectancy level. This demonstrates that the basic assumption of the correction-for-errors scoring formula (that all wrong responses are pure guesses) penalizes the student by utilizing only those responses of which he feels certain.

Chance Expectancy, Sample Size, Replacement and Non-Replacement Sampling

This study investigates the influence of sample size, non-replacement and replacement sampling on the number of MMPI items which will reach significance levels of .05, .01, and .001 purely by chance. The results show that replacement sampling of a VA NP population gives a more stable sampling distribution than non-replacement sampling. Larger sized samples seem to have a somewhat greater number of mean chance occurrences than smaller sized samples. The common procedure of requiring that more than 19 items of a 373-item MMPI have to reach significance at the .05 level before a non-chance occurrence is accepted is a definite underestimation according to the upper range limits of chance significances found in this study for samples of size 30, 40, 50, 100, 150, and 200. The best solution for a decision whether or not findings are non-chance occurrences would be to use a more stringent level of significance than the .05 level and co use the upper range limits of chance significances found in this study for the appropriate sample size. It is likely that different populations have associated with them different numbers of items which will reach chance significance.