What sample size would be needed to estimate the true propor

What sample size would be needed to estimate the true proportion of students at your college (if you are a student) who are wearing backpacks, with 95 percent confidence and an error of

Solution

so it\'s +/- z*sqrt(p*(1-p)/n)
so we want that to be equal to .04
if we don\'t know p, let it be .5
.04=1.96*sqrt(.5*.5/n)
(.04/1.96)^2=.25/n
reverse both sides we get
n/.25=(1.96/.04)^2
n=.25*(1.96/.04)^2
600.25 or 601