Which statement best describes the relationship between p-value and alpha?

Which statement best describes the relationship between p-value and alpha?

• A. If p-value is less than alpha, reject Ho
• B. If p-value is greater than alpha, reject Ho
• C. The p-value does not relate to alpha
• D. Alpha is derived from the p-value

Answer: (A)

The key idea is how we decide whether to reject the null hypothesis using a p-value and a pre-set significance level. The significance level (alpha) is chosen before looking at the data and represents the largest probability of a false positive we’re willing to accept. The p-value is the probability, under the null hypothesis, of getting results as extreme as or more extreme than what we observed. If that p-value falls below the chosen alpha, the observed result is unlikely enough under the null to consider the finding statistically significant, so we reject the null hypothesis. If the p-value is larger than alpha, the data don’t provide enough evidence to reject the null. The p-value is computed from the data, while alpha is set beforehand; they’re compared to make the decision. Often we see the threshold stated as p ≤ alpha, but the core idea is the same: small p-values relative to alpha lead to rejection of the null.

The key idea is how we decide whether to reject the null hypothesis using a p-value and a pre-set significance level. The significance level (alpha) is chosen before looking at the data and represents the largest probability of a false positive we’re willing to accept. The p-value is the probability, under the null hypothesis, of getting results as extreme as or more extreme than what we observed.

If that p-value falls below the chosen alpha, the observed result is unlikely enough under the null to consider the finding statistically significant, so we reject the null hypothesis. If the p-value is larger than alpha, the data don’t provide enough evidence to reject the null. The p-value is computed from the data, while alpha is set beforehand; they’re compared to make the decision. Often we see the threshold stated as p ≤ alpha, but the core idea is the same: small p-values relative to alpha lead to rejection of the null.