Assertion (A) Analysis

The assertion states that the hypothesis a researcher tests is the null hypothesis. In statistical hypothesis testing, researchers typically formulate a null hypothesis (denoted as $H_0$), which represents a statement of no effect or no difference. This is the specific hypothesis that is subjected to statistical analysis to determine if it can be rejected based on the collected data. Therefore, the assertion is true.

Reason (R) Analysis

The reason states that the alternative hypothesis (denoted as $H_1$ or $H_a$) is accepted only when the null hypothesis ($H_0$) is rejected. This aligns with the standard procedure of hypothesis testing. If the evidence from the sample data is strong enough to reject $H_0$ at a predetermined significance level, the conclusion drawn is typically in favor of the alternative hypothesis $H_1$. Therefore, the reason is true.

Relationship Analysis

While both the assertion (A) and the reason (R) are true statements regarding hypothesis testing:

• Assertion (A) identifies the object of testing (the null hypothesis).
• Reason (R) describes the logical consequence of the testing process concerning the alternative hypothesis (acceptance follows rejection of the null).

Reason (R) does not explain *why* the null hypothesis is the one formally tested (Assertion A). It explains what happens when the test result leads to rejecting the null hypothesis. The reason for testing the null hypothesis relates to the structure of statistical inference and the principle of falsification, not directly to the condition for accepting the alternative hypothesis. Thus, (R) is true, but it is not the correct explanation for (A).

Conclusion

Based on the analysis, both Assertion (A) and Reason (R) are true, but Reason (R) does not correctly explain Assertion (A).