At an alpha level of 0.05, what does this imply about the risk of Type I error?

At an alpha level of 0.05, what does this imply about the risk of Type I error?

• A. There is a 5% risk of a Type I error
• B. There is a 5% risk of a Type II error
• C. There is 95% power
• D. There is a 5% chance the study is invalid

Answer: (A)

The alpha level sets the maximum allowable probability of a Type I error, meaning the chance of incorrectly rejecting the true null hypothesis. With an alpha of 0.05, if the null hypothesis is actually true, about 5% of repeated studies would yield a statistically significant result just by random variation. This is not about the risk of a Type II error (failing to detect a real effect) or about the study being invalid; those relate to power (1 minus beta) and other aspects of study quality. So the statement that there is a 5% risk of a Type I error correctly reflects what the alpha level conveys.

The alpha level sets the maximum allowable probability of a Type I error, meaning the chance of incorrectly rejecting the true null hypothesis. With an alpha of 0.05, if the null hypothesis is actually true, about 5% of repeated studies would yield a statistically significant result just by random variation. This is not about the risk of a Type II error (failing to detect a real effect) or about the study being invalid; those relate to power (1 minus beta) and other aspects of study quality. So the statement that there is a 5% risk of a Type I error correctly reflects what the alpha level conveys.