For which of the following hypotheses is a one-tailed test of significance appropriate?
A) Teaching method A and teaching method B will produce different student achievement gains.
B) There is no difference in the effects of Head Start programs on the achievement gains of low-income Caucasian and African-American children.
C) The mean IQ score of a sample is significantly different from the population mean.
D) Children receiving a dietary supplement will show greater achievement gains than those receiving a placebo.

Question

Quizplus · Accepted Answer

A one-tailed test of significance is appropriate when the hypothesis predicts a direction of the effect, such as expecting one group to score higher or lower than another. Option D predicts that children receiving a dietary supplement will show greater achievement gains than those receiving a placebo, indicating a specific direction and thus making a one-tailed test appropriate. Options A, B, and C suggest comparisons without specifying a direction of difference or are testing for any significant difference, which would require a two-tailed test.

For Which of the Following Hypotheses Is a One-Tailed Test