Question

An independent research firm conducted a study of 100 randomly selected children who were participating in a program advertised to improve mathematics skills. The results showed no statistically significant improvement in mathematical skills, using a significance level of 0.05. The program is effective, which of the following would be an appropriate method for increasing power in this context?

a. Increase the sample size to 200 children.
b. Use a two-sided test instead of a one sided test.
c. Decrease the sample size.
d. Use alpha-0.01 instead of a-alpha.
e. Use a one sided test instead of a two-sided test.

Answer 1

b) use a two-sided test instead of a one sided test.

Explanation:

If we are using a significance level of 0.05, then the two-tailed test assigns half alpha to test for statistical significance in one direction and half alpha to test statistical significance in the other direction. This implies that .025 is present in each tail of the test statistical distribution. When using the two-tailed test, regardless of the direction of the relationship you assume, we test the possibility of the relationship in both directions.