Question

You measure 48 textbooks' weights, and find they have a mean weight of 54 ounces. Assume the population standard deviation is 11.7 ounces. Based on this, construct a 90% confidence interval for the true population mean textbook weight.

Give your answers as decimals, to two places

Answer 1

Solution :

Given that,

= 54

= 11.7

n = 48

At 90% confidence level the z is ,

= 1 - 90% = 1 - 0.90 = 0.10

/ 2 = 0.10 / 2 = 0.05

Z_/2 = Z_0.05 = 1.645

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

= 1.645 * (11.7 / 48)

=2.78

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

- E < < + E

54 - 2.78 < < 54 + 2.78

51.22< < 56.78

(51.22,56.78 )