Question

° F, 70° F, and 90° F) for the levels of stress to be included in the experiment. Because the experimenter worked at an all male school, only male participants were in the study. The task selected for the first experiment is a forced-choice reaction time task in which one of two stimuli requiring a quick response is presented on each trial. Participants are instructed to respond quickly and accurately.

The psychologist thinks that stress will lead to a decrease in reaction time. The psychologist does not have a lot of money in his grant so he decides to test each participant in each condition during the 90-minute testing session. Each participant is first tested in the 90° condition, then the 70° condition, and finally in the 40° condition. Each participant is given 30 trials per condition.

The results showed that the participant mean reaction times for the three conditions were as follows:

Temperature             Mean Reaction Time

40° F                        430 msec

70° F                        487 msec

90° F                        525 msec

Statistical analyses of the mean reaction times revealed that each of the three conditions was reliably different from the other two conditions. The researcher concluded that thermal stress increases reaction time (makes responses slower).

a) Should the researcher’s conclusion be accepted? Please explain with two distinct reasons

Answer 1

The researcher's conclusions should not be accepted for the following two reasons:

1. Since the sample comprised of only male participants from a particular school, the experiment lacks external validity. in other words, its findings cannot be generalized to the population at large because the sample is not representative.

2. Because the same set participants of were utilized in all three experimental conditions, carryover effects are highly likely to occur. In particular, the result that thermal stress increases reaction time may only be obtained because participants were exposed to the highest temperature condition first after which practice effects may have facilitated their performance on the other conditions.