The distribution of blood cholesterol level in the population of young men aged 20 to 34 years is close to Normal with mean 188 milligrams per deciliter (mg/dL) and standard deviation 41 mg/dL. You measure the blood cholesterol of 14 young men aged 20 to 34 years who have completed at least one marathon. The mean level is x = 172 mg/dL. Assume that σ is the same as in the general population.
We suspect that the mean μ for all young men aged 20 to 34 years who have completed at least one marathon is lower than that of the population of all young men aged 20 to 34 years. Thus, we decide to test the hypotheses H0: μ = 188, Ha: μ < 188. The z test statistic for testing these hypotheses is
a. 5.46
b. 1.46
c. -5.46
d. -1.46