Statistics Extra Practice

-These are hypothesis tests. You must determine which test to perform and which test statistic to calculate. Show all work, step by step, calculations labeled. Round to 2 decimal pages; do not round values obtained from tables.

Three problems:

1. A sample of freshmen takes a reading comprehension test and their scores are summarized below. If the mean for the general population on this test is ?=12, can you conclude that this sample is significantly different from the population?

Sample scores: 16, 8, 8, 6, 9, 11, 13, 9, 10

a. Conduct a hypothesis test with ?=.05.

b. Write up the results using APA format.

2. A psychologist studies the effect of frequent testing on perception of course material. In one of the professor’s sections, students are given quizzes each week. The second section receives only two tests during the semester. At the end of the semester, both sections receive the same questionnaire. Summarized below is a random sample of the perception scores from 9 students in each section.

Frequent Quizzes: 4, 8, 3, 10, 5, 6, 6, 2, 10

Two Exams: 5, 7, 9, 9, 10, 10, 12, 14, 14

a. Do the data indicate that testing frequency has a significant effect on performance? Conduct a hypothesis test with ?=.05.

b. Compute r2 to measure the size of the effect.

c. Compute a 90% confidence interval to estimate the population mean difference.

d. Write up your results using APA format.

3. A researcher would like to determine if relaxation training will affect the number of headaches for chronic headache sufferers. For a week prior to training, each subject records the number of headaches suffered. Subjects then receive relaxation training and for the week following training the number of headaches is again measured. The change in number of headaches before and after training (differences scores) is as follows (minus indicates a reduction in number of headaches):

Difference scores: -5, -1, -4, -3, -6, -8, 0, +1, -1

a. Is there an effect of relaxation training? Conduct a hypothesis test with ?=.05.

b. Compute Cohen’s d to measure the size of the effect.

c. Write up the results using APA format.