A new law was implemented in India to curb traffic violations by its citizens. A local police department wants to know if the law has been effective in decreasing the number of automobile accidents. They count the number of accidents for each day of the week in the week before and the week a month after the law was enacted. The results are in the following table.

Day Before After Monday 6 3 Tuesday 5 1 Wednesday 3 1 Thursday 5 8 Friday 7 3 Saturday 15 5 Sunday 7 8

a) Are the data paired? Explain.

b) Compute the mean difference.

c) Compute the standard deviation of the differences.

d) Compute the standard error of the mean difference.

e) Find the value of the t-statistic.

f) How many degrees of freedom does the t-statistic have?
g) Is the alternative one- or two-tailed? Explain.
h) What is the P-value associated with this t-statistic?
(Assume all conditions for inference are met.)
i) At a = 0.01, what is your conclusion?