Based on the distribution of the sample, which of the following are correct? (select all that apply.)
a. a z-test is appropriate since the sample standard deviation is given. since the data is almost normal, a t-test is appropriate.
b. a t-test is appropriate since the population standard deviation is given.
c. a z-test is appropriate since the sample size is smaller than 30.
d. a t-test is appropriate since the sample size is smaller than 30.
e. there are 15 degrees of freedom.
f. a t-test is appropriate since the population standard deviation is not known.
g. there are 16 degrees of freedom.