Confidence Interval for a Population Mean

Example 1.  The Minitab worksheet Sharks.mtw contains the lengths (in feet) of
44 sharks.  Find a 95% t confidence interval for the mean length of the shark population.

Example 2.  The Minitab worksheet cephalothin.mtw contains the potency measurements for
sixteen doses of the cephalosporin antibiotic cephalothin.  Find a 95% confidence interval
for the mean potency in the relevant cephalothin dose population. What assumptions are you making?
What is the correct interpretation of your interval and the correct interpretation of "95%" ?

Example 3. Find a 99% confidence interval for the mean cephalothin potency. Compare with the
interval in Example 1.


What Sample Size Do I Need ?

Example 4.  In Example 3 we got a 99% confidence interval for mean cephalothin
potency as (901.50, 914.00), which is an interval with margin of error 6.25.  The FDA wants
your next analysis on cephalothin to produce an interval with margin of error 4.0. at the same
desired confidence of 99%. What sample size (i.e. how many cephalothin doses) do you need
in your next analysis?