Final answer:
A two-tailed test is determined by the alternative hypothesis, Ha. If the alternative hypothesis states a difference or inequality between the two groups being compared, then it is a two-tailed test.
Step-by-step explanation:
A two-tailed test is determined by the alternative hypothesis, Ha. If the alternative hypothesis states a difference or inequality between the two groups being compared, then it is a two-tailed test.
For example, if the alternative hypothesis is Ha: μ ≠ 0, where μ is the population mean, it indicates a two-tailed test. This means we are interested in testing if there is a significant difference in both directions from the null hypothesis.
On the other hand, if the alternative hypothesis states a specific direction, such as Ha: μ > 0 or Ha: μ < 0, then it is a right-tailed or left-tailed test, respectively.