About what percent of couples in the U.S. today have difficulty conceiving a child?

Abigail is trying to figure out how she can BEST use employee pay to shape her employees' behavior. She is worried about consistent behavior, not speed. Therefore,

she is interested in getting a slow but steady rate of response from her workers. According to reinforcement principles, she should probably use a ______ schedule. a. fixed-ratio c. variable-ratio b. fixed-interval d. variable-interval

A psychologist observes the confrontation between two rival neighborhood gangs from the window of an abandoned building. This method of collecting observations is best described as

a. experimental regression. b. naturalistic observation. c. controlled experimentation. d. clinical case study.