Question

You read in the results section of an article in a psychology journal that the results of at-test for independent sample means revealed a significant t12 = 1.8, with σˆX1−X2 = 2. If there were 8 participants in the experimental group,

(a) how many participants were in the corresponding control group?

(b) what significance level was used, and was the test a one-tailed or a two-tailed test?

(c) what was the mean difference between the experimental and the control groups?

Answer 1

From the provided information, t₁₂=1.8, so the degree of freedom (df) = 12

a).

Let the number of participants in the corresponding control group = n₁

And the number of participants in the experimental group = n₂ which is given as 8.

Degree of freedom = 12

Thus, the number of participants in the corresponding control group = 6

b).

As, alpha () level of significance is not given but it can be assume as 0.05.

Since, the P value is not given it can not be find whether the test a one-tailed or a two-tailed but it can assume the test is two tailed.

c).

The mean difference between the experimental and the control groups can be obtained as:

As, and

Proceeding,

Thus, the mean difference between the experimental and the control groups was 3.6.