$4-6$ Assuming that the data shown in Table $4\mathrm{.}2$ were collected on a rural road in your state

and consideration is being made to set the speed limit on the road. Speed limits of $50,$

$55,60,$ and $65m\frac{i}{h}$ are being considered. Plot the expected non$-$compliance percent$-$

ages versus the associated speed limit on a graph and recommend the speed for the

road. Give reasons for your selection.

$4-7$ The accompanying data show spot speeds collected at a section of highway located in

a residential area. Using the student's $t$ test, determine whether there was a statisti$-$

cally significant difference in the average speeds at the $95\%$ confidence level.

$4-8$ Using the data furnished in Problem $4-7,$ draw the histogram frequency distribution

and cumulative percentage distribution for each set of data and determine $($a$)$ average

speed, $($b$)85$th$-$percentile speed, $($c$)15$th$-$percentile speed, $($d$)$ mode, $($e$)$ median, and

$($f$)$ pace.