Question

A group of statistics students decided to conduct a survey at their college to find the proportion of students who graduate. What is the required sample size to estimate, with a margin of error of .1 and a 80% confidence level, the proportion of students who graduate?

Answer 1

Solution :

Given that,

= 0.5

1 - = 1 - 0.5 = 0.5

Margin of error = E = 0.1  

At 80% confidence level the z is ,

= 1 - 80% = 1 - 0.80 = 0.20

/ 2 = 0.20 / 2 = 0.10

Z_/2 = Z_0.10 = 1.28

Sample size = (  Z_/2 / E)² * * (1 - )

= (1.28 / 0.1)² * 0.5 * 0.5

= 40.96 = 41

Sample size = n = 41