Question $1(25$ pts $.)$: The following table shows the ADT and number of crashes at six intersections before and after a

countermeasure was implemented to reduce crashes.

a$.$ What is the crash rate at intersection $3$ before a countermeasure was implemented to reduce crashes?

b$.$ What is the crash reduction $($CR$)$ factor of this countermeasure at intersection $3?$

c$.$ Determine if it can be concluded that this countermeasure is effective in reducing crashes at the following six

intersections. Assume $=0\mathrm{.}025$ and equal variance in the before and after samples. Clearly state your null and

alternative hypotheses, test statistic, critical value, and conclusion. The $t-$distribution table is provided on the last

page of the exam.