Question

You randomly sample 100 Publix customers. On average, it took these customers 3 minutes to check out. It is known that the standard deviation of the checkout time is one minute.

The sample mean will provide a margin of error of ____ if you use an alpha of .05.

a .196

b 0.10

c 1.96

d 2.08

Answer 1

Solution :

Given that,

Population standard deviation =    =1

Sample size n =100

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.96   ( Using z table )

Margin of error = E = Z/2 * ( /n)

= 1.96 * (1 / 100 )

=0.196

Margin of error = E = =0.196