Question

A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 520 babies were​ born, and 286 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?

Answer 1

We have given,              
              
x=286          
n=520          
Estimate for sample proportion=   0.55  
Level of significance is =1-0.99=0.01      
Z critical value(using Z table)=2.576      
              
Confidence interval formula

=(0.4938,0.6062)
              
Lower limit for confidence interval=0.4938  
              
Upper limit for confidence interval=0.6062  

Confidence interval contain 0.50 therefore, we fail to reject H0. Therefore, method does not appear to be effective.