Dr. Kang, a cognitive psychologist, conducts an experiment examining the effect of emotion on memory. He provides lists of 15 words to two groups of participants at his university. He puts the names of all the participants in a hat. The first 20 names he assigns to Group A and the last 20 he assigns to Group B. Group A is given a list of words that are very emotional in content (e.g., passion, murder). Group B is given a list of words that are neutral in content (e.g., houseplant, desk). He then measures how many words each group is able to remember after being distracted for 5 minutes by watching a video about the history of the university. He finds that Group A remembers 15% more words than Group B.
If Dr. Kang decided against using random assignment, which of the following would be threatened?
A)the covariance of the study
B)the temporal precedence of the study
C)the internal validity of the study
D)the external validity of the study

Question

Quizplus · Accepted Answer

Without random assignment, there could be pre-existing differences between the two groups that could affect the outcome, such as level of intelligence or memory ability. This threatens the internal validity of the study, which refers to the extent to which the study can confidently make causal claims.

Dr Kang, a Cognitive Psychologist, Conducts an Experiment Examining the Effect