Question

A random sample of 100 automobiles traveling on a section of an interstate showed an average speed of 60 mph. the distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph. refer to exhibit 8-3. if we are interested in determining an interval estimate for μ at 90.0% confidence, the z value to use is

Answer 1

The $(1-\alpha )100\%$ confidence interval for mean is

$\mu \pm z_{\alpha/2} \frac{\sigma}{\sqrt{n} }$.

Here $\alpha =0.1$.

Use standard normal distribution table.

The z value to be used is such that

$P(Z$

$P(Z$

z=-1.96

The z value to be used is 1.96.