Question

Optometrist Sean generally divides up his patient appointments for the day with mornings spent with clients who wear glasses, and clients who primarily wear contacts being in the afternoon.  He recently noticed that some of the patients that wear contacts want to be seen in the morning.  So he gives his 180 patients a take home survey that asks what time are they most available between 8 AM and 6 PM.  The data is interval, has a normal distribution, and the two samples have similar variances.  What test should be used to determine if there is a difference in preferred appointment time between patients who wear glasses and patients who wear contacts?

		Chi-square for Goodness of Fit
		Chi-square for Independence
		Mann-Whitney U
		Wilcoxon T
		Independent-measures t-test
		Repeated-measures t-test (paired-samples t-test)

Answer 1

In this case, assuming that distribution of the 180 patients between the glasses and the contacts groups is fairly even, and since it is also given that the two sample variances are also similar, so the best choice here would be a parametric test, since data is also already given to be normally distribubted.

The best test to be used in this case is Independent measures t-test, because the patients in the two groups answer the survey independently without being subject to any pre-or-post conditions.

So we can't use a paired t-test here.

The correct answer is Independent-measures t-test.