1 A clinical trial tests a method designed to increase the p

1. A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study

500 babies were born, and 275 of them were girls. Use the sample data to construct a

99% confidence interval estimate of the percentage of girls born.

Proportion p = 275/500 = 0.55

Standard Error = sqrt((0.55(1-0.55)) / 500 ) = 0.022

z for 99% = 2.575

CI = ( 0.55 - 2.575* 0.022 , 0.55 + 2.575* 0.022 )
= ( 0.493 , 0.607)

= ( 49.3% , 60.7%) Answer