Question

A random sample of 20 seniors from a large school district had a mean Math SAT score of 450 and a sample standard deviation of 85. Suppose we wanted to plan a similar study with just female seniors. We want to have a margin of error of 25 with 95% confidence. What is the sample size needed to achieve this margin of error? Assume that the standard deviation s = 100.

Answer 1

Solution :

Given that,

Population standard deviation = = 100

Margin of error = E = 25

At 95% confidence level the z is,

= 1 - 95%

= 1 - 0.95 = 0.05

/2 = 0.025

Z/2 = Z0.025 = 1.96  

sample size = n = [Z/2* / E] 2

n = [1.96 *100 / 25]2

n = 61.46

Sample size = n = 62

answered by: anonymous