In order to ensure that experimental and control groups are similar before the experiment begins, social scientists sometimes:

Nita is the office manager at a service station. two applicants, max and tim, arrive to interview for the open mechanic's position. max's clothes are dirty, his hair is unwashed, and he doesn't make eye contact when he gives nita his name. tim dresses in clean jeans and a nice shirt, is shaved, and shakes nita's hand when he introduces himself. after the interview, keith the head mechanic, asks nita what she thought. both men have the skill set needed for the position. nita recommends tim. she is responding to her perception of