11. Comparing Proportions
The form of the confidence interval is
where, as usual you can get from the last line of the t Distribution Table.
Example 11.2 : Using the data from Example 11.1, find the 95 confidence interval for .
Solution : The relevant numbers from Example 11.1 are: , , and , , .
Compute (after finding from the t Distribution Table)
with 95 confidence. (Note that this corresponds with the rejection of in Example 11.1 since 0 is not in the confidence interval.)