Question

If n=28, ¯xx(x-bar)=46, and s=7, find the margin of error at a 95% confidence level

Give your answer to two decimal places.

Answer 1

solution

Given that,

s =7

n = 28

Degrees of freedom = df = n - 1 =28- 1 = 27

At 95% confidence level the t is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

t /2,df = t0.025,27 = 2.052 ( using student t table)

Margin of error = E = t/2,df * (s /n)

= 2.052 * (7 / 28)

= 2.71

Margin of error = E = 2.71