Question

You measure 45 textbooks' weights, and find they have a mean weight of 51 ounces. Assume the population standard deviation is 7.7 ounces. Based on this, construct a 90% confidence interval for the true population mean textbook weight.

Give your answers as decimals, to two places

_________________ < μμ < __________________

Answer 1

Solution

Given that,

= 51

= 7.7

n = 45

At 90% confidence level the z is ,

= 1 - 90% = 1 - 0.90 = 0.10

/ 2 = 0.10 / 2 = 0.05

Z/2 = Z0.05 = 1.645

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

= 1.645 * (7.7 / 45)

=1.89

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

- E < < + E

51-1.89 < < 51 + 1.89

49.11 < < 52.89

( 49.11, 52.89 )