If the test value for the difference between the means of two large samples is 2.57 when the critical value is 1.96, what decision should be made?

A. Reject the null hypothesis.
B. Reject the alternative hypothesis.
C. Do not reject the null hypothesis.
D. Do not reject the equality hypothesis.



Answer :

To determine the correct decision for the hypothesis test, follow these detailed steps:

1. Identify the given values:
- Test value (also known as the test statistic): 2.57
- Critical value: 1.96

2. Understand the hypothesis test set-up:
- Null Hypothesis (H₀): This usually represents the statement that there is no effect or no difference. For example, it may state that the means of two samples are equal.
- Alternative Hypothesis (H₁): This usually represents the statement that there is an effect or a difference. For instance, it may state that the means of two samples are not equal.

3. Determine the decision rule:
- A common rule in hypothesis testing is to compare the test value to the critical value.
- If the absolute value of the test statistic is greater than the critical value, we reject the null hypothesis (H₀).
- If the absolute value of the test statistic is less than or equal to the critical value, we do not reject the null hypothesis (H₀).

4. Compare the test value to the critical value:
- The test value is 2.57.
- The critical value is 1.96.
- Check if 2.57 is greater than 1.96.

5. Make the decision:
- Since 2.57 is greater than 1.96, we reject the null hypothesis (H₀).

6. Select the correct answer based on the decision:
- Rejecting the null hypothesis corresponds to option A.

So the decision should be:
A) Reject the null hypothesis.