What critical value from Table D should be used to calculate the margin of error for a confidence interval for the mean of the population in each of the following situations?
A 95% confidence interval based on observations.
A 90% confidence interval from an SRS of 27 observations.
A 95% confidence interval from a sample of size 27.
These cases illustrate how the size of the margin of error depends on the confidence level and on the sample size. Summarize the relationships illustrated.