Question

Average pizza delivery times to the West Loop are normally distributed with an unknown population mean and a population standard deviation of six minutes. Students in 270 at UIC collect a random sample of 28 pizza deliveries to the West is taken and they find sample mean delivery time of 36 minutes. Find a 60 and 95 percent confidence interval for µ.

Answer 1

Solution :

Given that,

a) Z/2 = Z0.20 = 0.842

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

= 0.842 * ( 6 /  270 )

= 0.31

At 60% confidence interval estimate of the population mean is,

- E < < + E

36 - 0.31 <   < 36 + 0.31

( 35.69 <   < 36.31 )

b) Z/2 = Z0.05 = 1.645

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

= 1.645 * ( 6 /  270 )

= 0.60

At 90% confidence interval estimate of the population mean is,

- E < < + E

36 - 0.60 <   < 36 + 0.60

( 35.40 <   < 36.60 )