Confidence Interval
for a
Difference of Two Proportions

where

and

Notes:

• The confidence interval resulting from use of the above confidence limits is obtained by substituting the large sample pivotal quantity
  
  
  into the following (large sample) approximation
  
  
  and then rearranging terms in the inequality on the LHS until the desired interval is obtained.

Examples:

• See Example 13 in Johnson and Bhattacharyya (1996), pp. 442-443.