Question

Suppose the heights of a population of male giraffes are normally distributed with an unknown population mean and a population standard deviation of 3.4 feet. A random sample of male giraffes from the population produces a sample mean height of § = 15.2 feet.

What value of z should be used to calculate a confidence interval with a 90% confidence level?

Answer 1

Explanation:

Here we have:

90% confidence level:

α=1-0.90=0.10

`Z_(crit)=z_(\alpha /2)=z_(0.10/2)=1.645`

Hence the required Z value at 90% confidence level is 1.645