$4-26$

A county engineer would like to determine if a speed reduction strategy has been effec$-$

tive. She performs a second speed study to compare with one done before the strategy

was implemented. The collected data has the following characteristics.

$\frac{?}{\text{b}\text{a}\text{r}}(u{)}_1=43\mathrm{.}8m\frac{i}{h}$

$S_1=6\mathrm{.}5m\frac{i}{h}$

$n_1=30$

$\frac{?}{\text{b}\text{a}\text{r}}(u{)}_2=35\mathrm{.}2m\frac{i}{h}$

$S_2=7\mathrm{.}6m\frac{i}{h}$

$n_2=30$