Question

You are interested in studying the effect of laptops in class on students’ performance. At the beginning of the quarter, you randomly assign your 250 students to sit on either the left half or the right half of the lecture hall. Students on the left half are told to bring laptops to class and to take notes on their laptops. Students who sit on the right side of the room are required to write notes on paper. At the end of the quarter, you compare their performance on the final exam, and find that the n = 125 students in the laptop group got an average score of 84% on the exam (SD = 8%), and the students in the longhand group got an average score of 80% on the exam (SD = 7%).

1. Compute a t-statistic to compare the two groups’ performance.

2. Compute the standardized effect size.

3. Interpret the effect size you computed in the previous question. What, precisely, does that number mean?

Answer 1

1. t - test for two indepdent sample means:

Steps:

(1) Null and alternative hypothesis;

H0: the effect of laptops in class on students’ performanc is not increased

H1: the effect of laptops in class on students’ performanc is increased

i.e.

Thus we conclude that the effect of laptops in class on students’ performanc is increased

2)

3) It is medium effect size . This means that if two groups' means don't differ by 0.53 standard deviations or more, the difference is trivial, even if it is statistically significant.