Question

Find the minimum sample size you should use to assure that your estimate will be within the required margin of error around the population proportionIf you want to estimate the percentage of adults who have a paid subscription to a printed newspaper, how many adults must you survey if you want 90% confidence that your percentage has a margin of error of three percentages points?

Answer 1

Solution :

Given that,

= 0.5

1 - = 0.5

margin of error = E = 3% = 0.03

At 90% confidence level

= 1 - 90%  

= 1 - 0.90 =0.10

/2 = 0.05

Z/2 = Z0.05 = 1.645 ( Using z table )

Sample size = n = (Z/2 / E)2 * * (1 - )

= (1.645 / 0.03)2 * 0.5 * 0.5

=751.67

Sample size = 752