6. You are constructing a 90% confidence interval for a sample consisting of n = 9 values and an

unknown population standard deviation. The population appears to be very skewed. Determine

whether a margin of error should be calculated using a critical value of za/2, a critical value of ta/2, or neither.

a) a critical value of za/2

b) a critical value of ta/2

c) neither

7. The standard deviation of sample size of n = 15 is 345 and the mean is 6784. Given that the population follows a normal distribution, construct a 90% confidence interval estimate of the mean of the population.

a) 6519
b) 6593
c) 6627
d)6783