Two-tailed test is which of the following?

Two-tailed test is which of the following?

• A. A test of a directional hypothesis.
• B. A test for equality of variances.
• C. A test that checks for an effect only in the positive direction.
• D. A test of a non-directional hypothesis.

Answer: (D)

A two-tailed test assesses evidence against the null in both directions. The alternative states that the parameter differs from the null value, without specifying which direction the difference goes. Because the sampling distribution under the null is symmetric, you consider extreme results in both tails and multiply the one-tailed p-value by two. This makes it a non-directional test: you’re looking for any difference, whether positive or negative. This is not about testing equality of variances, nor about effects in only one direction—that would be a one-tailed test. So a two-tailed test is best described as a non-directional hypothesis test.

A two-tailed test assesses evidence against the null in both directions. The alternative states that the parameter differs from the null value, without specifying which direction the difference goes. Because the sampling distribution under the null is symmetric, you consider extreme results in both tails and multiply the one-tailed p-value by two. This makes it a non-directional test: you’re looking for any difference, whether positive or negative. This is not about testing equality of variances, nor about effects in only one direction—that would be a one-tailed test. So a two-tailed test is best described as a non-directional hypothesis test.