TYPE-II ERRORS IN COMPARISONS OF DEXTRAL AND SINISTRAL GROUPS

Anomalous cerebral dominance can have multiple manifestations, e.g., l eft-eye preference or left-foot preference in the absence of left hand edness per re. The 1987 estimate of prevalence of anomalous dominance in the population by Geschwind and Behan approaches 30%, three times t he estimate obtained by using handedness alone as the sorting criterio n. Accordingly, substantial numbers of subjects assigned to ''dextral' ' groups may actually display other legitimate indicators of anomalous dominance. As such there is a tendency to commit Type II errors in st udies in which handedness alone is used to represent the Variance attr ibuted to cerebral dominance. Accordingly, null hypotheses assessing t he relations of cerebral dominance with dependent variables are accept ed even though they may, in fact, be false.