Question

In a random sample of eight people the mean commute time to work was 35.5 minutes, and the SD was 7.2, find the t distribution to find the mean margin or error, given 95% confidence intervals for the population mean.

Answer 1

Solution :

Given that,

s =7.2

n =8 Degrees of freedom = df = n - 1 =8 - 1 = 7

a ) At 95% confidence level the t is ,

= 1 - 95% = 1 - 0.95 = 0.05

  / 2= 0.05 / 2 = 0.025

t /2,df = t0.025,7 = 2.365 ( using student t table)

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

= 2.365 * (7.2 / 8)

E= 6.0203

Margin of error = E =6.0203