Question

A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 480 babies were born,
and 264 of them were girls. Use the sample data to construct a 99% confidence interval estimate of the percentage of girls
born. Based on the result, does the method appear to be effective?

< p < (Round to three decimal places as needed.)
Does the method appear to be effective?
Yes, the proportion of girls is significantly different from 0.5.
No, the proportion of girls is not significantly different from 0.5.

Answer 1

The 99% confidence interval for population proportion (p) is

That is

where

264 / 480 = 0.55

For 99% confidence , zc = 2.56

Therefore 99% confidence interval estimate of proportion of girls

= 0.55 - 0.0581 < p < 0.55+ 0.0581

= 0.492 < p < 0.608

As the confidence interval includes 0.5 ( that means p can take value 0.5)

Thus answer is

No , proportion of girls is not significantly different from 0.5