Question: Define Type I error and Type II error, and identify the type of error that researchers control.

• We can decide to retain or reject a null hypothesis, and this decision can be correct or incorrect. Two types of errors in hypothesis testing are called Type I and Type II errors.

• A Type I error is the probability of rejecting a null hypothesis that is actually true. The probability of this type of error is determined by the researcher and stated as the level of significance or alpha level for a hypothesis test.

• A Type II error is the probability of retaining a null hypothesis that is actually false.