Should we use t? Determine whether we can safely use a t* critical value to calculate a confidence interval for the population mean in each of the following settings.

(a) We collect data from a random sample of adult residents in a state. Our goal is to estimate the overall percent of adults in the state who are college graduates.

(b) The coach of a college men’s basketball team records the resting heart rates of the 15 team members. We use these data to construct a confidence interval for the mean resting heart rate of all male students at this college.

(c) Do teens text more than they call? To find out, an AP® Statistics class at a large high school collected data on the number of text messages and calls sent or received by each of 25 randomly selected students.

The Fathom boxplot below displays the difference

(texts − calls) for each student.

-20 0 20 40 60 80 100 120 diff