Wilcoxon rank-sum test

a statistical test of centrality for ranked data that compares the median values of two independent samples to determine whether they have been drawn from the same population. In this nonparametric equivalent of the t test, one combines the data points from the different groups into a single pool and ranks their values in ascending order. The ranks that have been assigned are, in turn, used to determine the test statistic, W, which is evaluated for statistical significance. The calculations involved in the Wilcoxon rank-sum test are nearly identical to those for the Mann–Whitney U test. [Frank Wilcoxon]

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Psychology term of the day

July 27th 2024

object constancy

1. in object relations theory, the ability of an infant to maintain an attachment that is relatively independent of gratification or frustration, based on a cognitive capacity to conceive of a mother who exists when she is out of sight and who has positive attributes when she is unsatisfying. Thus, an infant becomes attached to the mother herself rather than to her tension-reducing ministrations; she comes to exist continuously for the infant and not only during instances of need satisfaction. This investment by an infant in a specific libidinal object indicates that he or she no longer finds people to be interchangeable.

2. see perceptual constancy.