n=200, x=40, 95%confidence Use the sample data and confidence level to construct the confidence interval estimate of the population proportion p.
A confidence of 95% implies that `alpha=.05,alpha/2=.025`
`z_(alpha/2)=1.96` from a table.
The interval we seek is given by:
`.2-1.96sqrt((.2(.8))/200)<p<.2+1.96sqrt((.2(.8))/200)` or approximately:
Thus, with 95% confidence, we can say that 14.5%<p<25.5%