PRACTICE ANOTHER

Suppose the distribution is normal. $($Round your answers to four decimal places.$)$

$($a$)$ Calculate $P(69\stackrel{}{x}71)$ when $n=9.$

$($b$)$ How likely is it that the sample mean diameter exceeds $71$ when $n=25?$

You may need to use the appropriate table in the Appendix of Tables to answer this question.