Sample size for estimating the population proportion 2

Sample size for estimating the population proportion: 2 n=p(1 – p )(z /E ) Sample size for estimating the population mean: n= (zσ/E) ������� � ��� : ����� 2

Sample size for estimating the population mean: ������� � ��� : �����

EXAMPLE: A population is estimated to have a stander deviation of 10. We want to estimate the population mean within 2, with a 95 percent level of confidence. How large a sample is required? ? σ=10 , E=2 , 95% Z=1. 96 we must use this formula: n= (zσ/E) 2 n=(1. 96 x 10 / 2 ) 2 n=97 ������� � ��� : �����

Sample size for estimating the population proportion: ������� � ��� : �����

EXAMPLE: The estimate of the population proportion is to be within. 05 , with a 95 percent level of confidence. The best estimate of the population proportion is. 15. How large a sample is required? E=. 05 , 95% z=1. 96 , p=. 15 we must use this formula: n=p(1 – p )(z /E ) 2 2 n=. 15( 1 -. 15 )(1. 96/. 05) n=( 0. 1275 )(1536. 64) n= 196 ������� � ��� : �����