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 u and standard deviation

b. Random sample of size n = 135 from a normal distribution

with unknown mean u and standard deviation

c. Random sample of size n = 10 from a normal distribution

with unknown mean u and standard deviation

= 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