Pedro was working on a report on Swiss and Austrian psychiatrists. He decided to find a 90 percent confidence interval for the difference in mean age at the time of significant psychiatric discoveries for Swiss versus Austrian psychiatrists. He found the ages at the time of psychological discovery of all the members of both groups and found the 90 percent confidence interval based on a t-distribution using a calculator. The procedure he used is not appropriate in this context because a
The sample sizes for the two groups are not equal.

b
The entire population is measured in both cases, so the actual difference in means can be computed and a confidence interval should not be used.

c
Age at the time of psychological discovery occurs at different intervals in the two countries, so the distribution of ages cannot be the same.

d
Age at the time of psychological discovery is likely to be skewed rather than bell shaped, so the assumptions for using this confidence interval formula are not valid.

e
Age at the time of psychological discovery is likely to have a few large outliers, so the assumption for using this confidence interval formula is not valid.