A state department of the tourism and recreation gathers data on the number of cars with out of state license plates in state park. (The group's position is that more out-of-state plates mean the state's advertising programs are working.) The sample size is fixed at the n=90 each day. Data from previous 20 days point out the following number of out-of-state license plates:
|
Day
|
Out-of-state Plates
|
|
1
|
24
|
|
2
|
33
|
|
3
|
18
|
|
4
|
21
|
|
5
|
26
|
|
6
|
31
|
|
7
|
15
|
|
8
|
18
|
|
9
|
23
|
|
10
|
13
|
|
11
|
22
|
|
12
|
15
|
|
13
|
25
|
|
14
|
33
|
|
15
|
16
|
|
16
|
22
|
|
17
|
34
|
|
18
|
10
|
|
19
|
23
|
|
20
|
13
|
a. Evaluate the entire proportion of "tourists" (cars with out-of-state plates).
b. Evaluate the UCL and LCL for these data.
c. Mention the control chart. Are all points in the control limits?
d. What action do you recommend for improving this procedure?