Previous studies on sleep tendencies report that, on average, an adult American will sleep for 6 hours each night with a standard deviation of 0.75 hours. You survey a SRS of 100 adult Americans and determine that the mean sleep time is 5 hours. Which Hypothesis Test should be used here?
a. One-sample t-test for means.
b. One-sample z-test for means.
c. One sample z-test for proportions.
d. One sample t-test for proportions.
e. Chi-squared goodness of fit test.