= M - ^sM ^sM = s = S²

n n

S² = SS

n - 1

1. Verbally explain Type I and Type II error. What symbols do we use to identify Type I and Type II errors?

2. In a PSY-101 class, a teacher is interested in seeing if merely having students sign in everyday in class will increase attendance. Over many prior semesters of PSY-101 teaching, it has been found that the average number of classes students attend is = 24 of 30 during the semester. One semester the teacher institutes a sign in sheet on which students sign in each day. At the end of the semester, in a classroom of n=49 students, the students have attended an average of M=28 classes. The teacher finds that the standard deviation for the sample of 49 students was s=11.50. Did the use of the sign-in sheet significantly improve attendance. Test the hypothesis that the sign-in sheet changes attendance.

3. Under what circumstances is it necessary to do t-test, rather than a z-test?

4. As sample size increases, how does the shape of the t-distribution change?

5. Professor McGonagall is curious as to whether extra tutoring sessions for Transfiguration students can do more than just teach Transfiguration. Rather, she also wonders if the tutoring sessions can change confidence in ability to do all spells. There is a standardized test that measures students' confidence in spells with a = 32 for all Hogwarts students. Professor McGonagall teaches a special section of Transfiguration that includes bringing all students in for extra tutoring. In all, n=6 students participate, and Professor McGonagall measures spell confidence at the end of the semester. Test the hypothesis that the extra tutoring sessions changed spell confidence. Use = .01. Below are the scores of the 6 students on spell confidence at the end of the semester. Note: you only have raw data here. You will need to compute the sample mean and variance or standard deviation.

Spell Confidence Scores: 37, 28, 31, 35, 42, 27.