Final answer:
A Type I error in the context of the principal's claim about test scores would occur if the null hypothesis is rejected when it is actually true, which corresponds to option 1) Rejecting the null hypothesis when it is true.
Step-by-step explanation:
When conducting a hypothesis test, committing a Type I error or a Type II error affects the integrity of the test's conclusions. A Type I error occurs when the null hypothesis is incorrectly rejected. Specifically, for the middle school principal's claim, a Type I error would result from rejecting the null hypothesis that the standard deviation of seventh-graders' test scores is at least 14.7 when it is actually true.
The correct answer for identifying the Type I error is: 1) Rejecting the null hypothesis when it is true.