Question

Silverman and Eals (1992) were interested in exploring sex differences in spatial ability. Based on a theory about sexual division of labor in evolutionary history, Silverman and Eals proposed that females may perform better than men on tasks of spatial memory. In one test, 20 women and 21 men were placed in a room in which there were a number of objects. Later, they were asked to recall the objects in the room and where they were. Women remembered an average of 11.55 items (s = 5.23). Men remembered an average of 6.80 items (s = 4.34).

What is the null hypothesis for this study?

		Evolution has not affected the spatial memory of men and women
		Men remember what objects were present, but not where they were located
		Women do not perform better than men
		Women perform better than men

In a study comparing the effectiveness of two treatments, 30 people were randomly assigned to the first treatment and a different group of 30 people were randomly assigned to the second treatment for a total of 60 people. If you were to conduct a t test on the resulting data, how many degrees of freedom would your t have?

		28
		59
		29
		58

Imagine that the average sentence length of a total of 500 prisoners is 4.2 years. The warden randomly sampled 20 prisoners and recorded their sentence. And then he repeated this procedure three more times. The means and standard errors are as follows. Which sample estimate shows the least sampling variability?

		Sample one: mean=4.2, SE=5
		Sample three: mean= 3.7, SE=3
		Sample four: mean= 4.6, SE=4
		Sample two: mean=6, SE=2

Imagine you have a population of 100,000 cases. Which of the following degrees of freedom gives you the closest estimation of the population parameter?

		1000
		5
		10
		4

Answer 1

Null hypothesis is against the claim "females may perform better than men on tasks of spatial memory". So, null hypothesis is females may perform same as men on tasks of spatial memory.

Thus, null hypothesis for this study is Evolution has not affected the spatial memory of men and women

Degree of freedom = n1 + n2 - 2 = 30 + 30 - 2 = 58

Least sample variability is with least standard errors. So, the correct answer is Sample two: mean=6, SE=2

For a population of 100,000 cases, degree of freedom should be a large number. So, the answer is 1000.