In each of the following instances, determine whether you would use a z- or t-statistic (or neither) to form a 95% confidence interval and then look up the appropriate z- or t-value.
a. Random sample of size n = 23 from a normal distribution with unknown mean m and standard deviation σ
b. Random sample of size n = 135 from a normal distribution with unknown mean μ and standard deviation σ
c. Random sample of size n = 10 from a normal distribution with unknown mean m and standard deviation s = 5
d. Random sample of size n = 73 from a distribution about which nothing is known
e. Random sample of size n = 12 from a distribution about which nothing is known