Armand conducts a study for his research method class. He is curious as to whether watching romantic movies makes people more committed to their romantic relationship. He collects a sample of men in dating relationships and divides them into two groups. One group watches a 5-minute clip of a movie in which the main characters are having a romantic first date. The second group watches a 5-minute clip from the same movie in which the main characters break up. After the participants watch the movie clip, they are then asked to write a sentence about their relationship. Armand counts the number of uses of the words we and us as a measure of commitment. After conducting the study, he finds that there is not a statistically significant difference between his two groups. 1. Provide three reasons why Armand's study may have resulted in null effects.
2. Armand's professor suggests that the null effect may be due to insufficient between-group variance. Describe two ways that Armand's study may have had poor between-group variance.
3. Armand's professor suggests that the null effect may be due to a large amount of within-group variance. State three causes of within-group variance in Armand's study.
4. Armand's professor proposes that he replicate the study and double the number of participants he recruits. State which cause(s) of within-group variability will be helped by adding more participants and why this will help.