A health science researcher believes that athletes have a lower resting heart rate than the general population. He knows, for the general population, that μ = 78 and σ = 9. He is planning to do a study in which he obtains a random sample of athletes, measures their resting heart rates, and uses a single-sample z test to see if the mean heart rate for the sample of athletes is lower than the general population mean.

(a) Should he do a one-tailed test or a two-tailed test?

(b) Write the null and alternative hypotheses.