Question

According to the National Health Statistics Reports, a sample of 33 men aged 20–29 years had a mean waist size of 36.9 inches with a sample standard deviation of 8.8 inches. What is our margin of error for a 95% confidence interval? Round to 3 decimal places

Answer 1

Solution :

Given that,

s =8.8

n =33

Degrees of freedom = df = n - 1 =33 - 1 = 32

At 95% confidence level the t is ,

= 1 - 95% = 1 - 0.95 = 0.05

  / 2= 0.05 / 2 = 0.025

t /2,df = t0.025,32 = 2.037 ( using student t table)

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

= 2.037* ( 8.8/ 33)

= 3.120

Margin of error = E = 3.120