A city wants to know if a new advertising campaign to make citizens aware of the dangers of driving after drinking has been effective. They count the number of drivers who have been stopped with more alcohol in their systems than the law allows for each day of the week in the week before and the week a month after the campaign starts. Here are the results:
|
Day of week
|
Before
|
After
|
|
M
|
5
|
2
|
|
T
|
4
|
0
|
|
W
|
2
|
2
|
|
Th
|
4
|
1
|
|
F
|
6
|
8
|
|
S
|
14
|
7
|
|
Su
|
6
|
7
|
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-sided? Explain.
h) What is the P-value associated with this t-statistic? (Assume that the other assumptions and conditions for in- ference are met.)
i) At a = 0.05, what do you conclude?