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The power of a test is influenced by the sample size and the choice of significance level. a. Explain how increasing the sample size affects the power (when significance level is held fixed). b. Explain how increasing the significance level affects the power (when sample size is held fixed).

Short Answer

Expert verified
Increasing both the sample size and the significance level increases the power of a test. The larger sample size reduces the variability which makes it easier to detect a difference. Similarly, a larger significance level expands the rejection region making it more likely to reject the null hypothesis if it's false.

Step by step solution

01

Explain the impact of sample size on power

Increasing the sample size while holding the significance level constant generally increases the power of a test. This is because a larger sample size gives more information, which makes it easier to detect a difference if one truly exists. In more technical terms, as the sample size increases, the variability or standard error of the sample mean decreases, which means the test statistic is more likely to fall in the rejection region if the null hypothesis is false.
02

Explain the impact of significance level on power

Increasing the significance level (i.e., the probability of rejecting the null hypothesis when it is true, or the Type I error rate) while holding the sample size constant also generally increases the power of the test. This is because by allowing for a larger chance of incorrectly rejecting the null hypothesis (increasing Type I error), we also increase our chances of correctly rejecting the null hypothesis when it is false (thereby increasing power). Essentially, when we increase the significance level, we expand the rejection region, which makes it more likely that we'll reject the null hypothesis if it is false.

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