In: Statistics and Probability
In a group of 227 taking an experimental pill, 52 developed nausea. In a group of 45 taking a placebo, 5 developed nausea. Construct a 95% confidence interval estimate for the difference between the proportion of nausea for those taking the pill and those taking the placebo.
The 95% Confidence Interval for Proportions
For Experimental Pill: = 52/ 227 = 0.2291, 1 - = 0.7709, n1 = 227,
For the Placebo: = 5/ 45 = 0.1111, 1 - = 0.8889, n2 = 45,
The Z critical (2 tail) for = 0.05, is 1.96
The Confidence Interval is given by (- ) ME, where
(- ) = 0.2291 – 0.1111 = 0.118
The Lower Limit = 0.118 - 0.1069 = 0.0111
The Upper Limit = 0.118 + 0.1069 = 0.2249
The 95% Confidence Interval is (0.0111 , 0.2249)