Statistics
posted by Jon .
142 out of 507 people were right. Calculate a 95% confidence interval for the proportion of the entire population that could be right. I did some of the work and got .72...don't know what to do with this? Please help.

p = 142/ 507 = 0.28
SD = sqrt(p(1p)/n)
0.28+ 0.039
(.241, .319) 
so I could say that with 95% confidence, between 24.1% and 31.9% of the entire population could be right?

you know I am getting .0199 SD =srt(.28(1.28)/506 = .0119? Please check for me again?

YES. IF YOUR PROFESSOR SAID THAT YOUR ANSWER SHOULD BE IN PERCENT.
P = 142/507 = 0.28
SD = SQRT( .28*.72/507)
SQRT(0.2016/507) = 0.0199
Z = 1.96
0.28+1.96*0.0199
0.28+ 0.039
( 0.241, 0.319) 
I get it now...I was missing a step too! Thanks Much!