Question

two researchers conducted a study in which two groups of students were asked to answer 42 trivia questions from a board game. the students in group 1 were asked to spend 5 minutes thinking about what it would mean to be a professor, while the students in group 2 were asked to think about soccer hooligans. these pretest thoughts are a form of priming. the 200 students in group 1 had a mean score of 24.7 with a standard deviation of 4, while the 200 students in group 2 had a mean score of 16.1 with a standard deviation of 3. complete parts (a) and (b) below
a. the researchers are 90% confident that the difference of the means is in the interval
b. there is a 90% probability that the difference of the means is in the interval
c. the researchers are 90% confident that the difference between randomly selected individuals will be in the interval
d. there is a 90% probability that the difference between randomly selected individuals will be in the interval
(b) what does this say about priming?
a. since the 90% confidence interval does not contain zero, the results suggest that priming does not have an effect on scores.
b. since the 90% confidence interval contains zero, the results suggest that priming does not have an effect on scores.
c. since the 90% confidence interval does not contain zero, the results suggest that priming does have an effect on scores.
d. since the 90% confidence interval contains zero, the results suggest that priming does have an effect on scores.

Explanation:

• Confidence interval: A confidence interval gives a range of values within which the true population parameter (in this case, the difference in means) is likely to lie. A 90% confidence interval means that if we were to repeat the study many times, about 90% of the intervals would contain the true difference in means.
• Effect of priming: If the confidence interval does not contain zero, it suggests that there is a statistically significant difference between the two groups. Since group 1 (primed to think about being a professor) had a higher mean score than group 2 (primed to think about soccer hooligans), and the confidence interval does not contain zero, this indicates that priming has an effect on scores.

Answer:

C. Since the 90% confidence interval does not contain zero, the results suggest that priming does have an effect on scores.