Question

If n=29, ¯x(x-bar)=39, and s=5, find the margin of error at a 80% confidence level

Give your answer to two decimal places.

Answer 1

Solution :

Given that,

= 39

s =5

n = 29

Degrees of freedom = df = n - 1 =29 - 1 = 28

a ) At 80% confidence level the t is ,

= 1 - 80% = 1 - 0.80 = 0.20

  / 2= 0.10

t /2,df = t0.10,28 = 1.313 ( using student t table)

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

= 1.313 * (5 / 29)

E=1.22

Margin of error = E =1.22