Latona did an experiment at a military barracks over the space of a few months to examine the effect of group size on group morale. he randomly assigned soldiers to the experimental and control groups and did a pretest and posttest. midway through the experiment, there was an incident in a nearby city involving some soldiers in which the soldiers were visibly mistreated by the community, which affected the morale of both the experimental and control groups. which source of internal invalidity does this example reflect?
a. historyb. maturationc. instrumentationd. selection biasese. compensation