Question

A critical trial tests a method designed to increase the probability of conceiving a girl. In the study 300 babies were born, and 270 of them were girls. Use the sample data to construct a 99% confidence interval estimate of the percentage of girls born (?<p<?). Based on the result, does the method appear to be effective? yes or no.

Answer 1

x                    =				270
sample size		n                    =		300
sample proportion     p̂		x/n=		0.9000
std error       =Se		=√(p*(1-p)/n) =		0.0173
for 99 % CI value of z=				2.5758
margin of error E=z*std error                            =				0.0446
lower confidence bound=sample proportion-margin of error				0.855
Upper confidence bound=sample proportion+margin of error				0.945

from above 99% CI: 0.855<p<0.945

as confidence interval contain all values above 0.5 level ; tehrefore  method appear to be effective. Yes