Which table should be used to determine a confidence interval on the mean when standard deviation is NOT known and the sample size is 10?

Periodically, a sample of 20 items are randomly selected from a population that is normally distributed, the average is computed, and plotted. Which of the following statements is correct?
. The average of the logarithms of the values is lognormally distributed.
. The standard deviation of the averages is equal to the standard deviation of the individuals divided by the square root of 20.
. The variance of the averages is equal to the variance of the individuals divided by the square root of 20.

The audit team normally advises the auditee immediately upon the discovery of a finding during an audit.
Which of the following items is (are) valid reasons for taking this action?
I. If corrected immediately, the findings may be eliminated from the audit report.
II. If corrected immediately, it shows genuine auditee interest in the objectives of the audit.
III. If corrected immediately, it demonstrates the strength of an ongoing audit program.

Information that is received by upper management, is often distorted. Which of the following actions is effective in countering this problem?
I. Stop killing the messenger.
II. Establishing an open door policy.
III. Practice management by walking around.

You have been asked to sample a lot of 500 units from vendor whose past quality has been about 2% defective. A sample of 40 pieces is drawn from the lot and you have been told to reject the lot if you find two or more parts defective. What is the probability of finding two or more parts defective?