The variance of a population is symbolized by which of the following?

Participation in extracurricular activities is related to

A) reduced self-confidence and poorer self-images. B) decreased likelihood that they will participate in formal groups and organizations as adults. C) lower levels of self-efficacy. D) higher levels of self-esteem for adolescents.

By about eighteen months of age, an infant can solve ________ displacement problems, but not ________ displacement problems

A) physical; mental B) mental; physical C) invisible; visible D) visible; invisible