Chapter 10 Quiz Review

A research design that uses a separate sample for each treatment condition is called an independent-measures research design or a _____ design.

• Within Subjects

• Between Treatments

• Between Subjects

• Within Treatments

An independent-measures t statistic is used to evaluate the mean difference between two treatments with n = 8 in one treatment and n = 12 in the other. What is the df value for the t statistic?

• 19

• 20

• 18

• 22

Answer explanation

Since we are dealing with two separate samples, we must add all participants and then subtract 2 degrees of freedom: 8 + 12 = 20 - 2 = 18.

Which of the following is the correct formula for pooled variance?

A research report states that there is a significant difference between treatments for an independent-measures design with t(28) = 2.27. Should the report state that...

• p > .05

• p < .05

Answer explanation

Since the researcher found significance, in their treatment, their report should state p < .05.

A psychologist predicts that the verbal skills of girls are higher when compared to boys. What is the t critical value if the psychologist took a sample of 5 girls and 5 boys with an alpha level of α = .01?

• 2.896

• -2.896

• 1.96

• 2.131

Answer explanation

Since the psychologist is expecting girls to score higher, it indicates a one-tailed hypothesis test. Given an alpha level of .01 and 10 kids in total, we calculate a df = 8. Now when we look at the one-tailed column of our t-table and match it with an alpha level of .01 and df = 8, we will see our critical value is t = 2.896

One sample from an independent-measures study has n = 6 with SS = 400. The second sample has n = 9 and SS = 770. What is the pooled variance?

• s_p ² = 90

• s_p ² = 176.25

• s_p ² = 78

• s_p ² = 88

How much difference should you expect between two population means?

• 0 point difference

• 1 point difference

• 2 point difference

• 3 point difference

Answer explanation

We shouldn't expect any difference between two population means. This is why, theoretically, the expected value is 0.

• True

• False

Why do we pool the variance for an independent-measures test?

• To give more weight to the bigger sample.

• To make our sample sizes even for t obtained

• To eliminate any weight given to the bigger sample

• None of the above

In a sample where n₁ = 3 corresponds to s² ₁= 10 and n₂ = 9 corresponds to s² ₂= 6, calculate the estimated standard error for this problem.

• s_{(M1 - M2)} = 2

• s_{(M1 - M2)} = 1

• s_{(M1 - M2)} = 1.63

• s_{(M1 - M2)} = 2.25