1. A lecturer wants to compare the exam results of students who complete their assign- ments with those who do not. A sample of nine students who have a good assignment completion record and nine students who do not are chosen from a class. The results of their statistics examination are given below:

Complete assignments 72.5 64 62.8 89.9 42.1 59.6 92 74.2 67 do not complete assignments46.4 52.9 82 34.1 40.0 67.2 76 55 39.1

Summary Statistics x s

Complete assignments 69.34 54.74

Do not complete assignments 15.34 16.99

1.Do these data provide evidence at the 5% significance level (= 0.05) that students who complete assignments get higher examination results? Include in your answer a clear statement of the hypothesis being tested.

2.What assumptions did you make to carry out the above test?

3.Construct and interpret 95% confidence interval for the true mean difference in scores between students who complete assignments and students who do not.