Question

If n=22, ¯xx(x-bar)=41, and s=2, find the margin of error at a 90% confidence level

Give your answer to two decimal places.

Answer 1

solution

Given that,

= 41

s =2

n = 22

Degrees of freedom = df = n - 1 =22 - 1 = 21

At 90% confidence level the t is ,

= 1 - 90% = 1 - 0.90 = 0.1

/ 2 = 0.1 / 2 = 0.05

t /2,df = t0.05,90 = 1.721 ( using student t table)

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

= 1.721 * (2 / 22) = 0.73