What is the p-value?

• A. The probability that the result would occur if the null hypothesis is true
• B. The probability that the alternative hypothesis is true
• C. The standard deviation of the sampling distribution
• D. The mean of the population

Answer: (A)

The p-value tells you how compatible the observed data are with the assumption that the null hypothesis is true. It is the probability, under the null, of obtaining a result as extreme as the one observed (or more extreme). A small p-value suggests the data are unlikely if the null is true and provides evidence against the null at your chosen significance level. It does not represent the probability that the null or alternative hypotheses are true, and it is not a measure of a population’s standard deviation or mean.