Xbar and Range Charts
The Highway Patrol has a target of 28 traffic tickets per week with standard deviation 5 tickets per week for a stretch of mountain highway. The number of tickets issued for 15 consecutive weeks is given below. t = number of week, x = number of tickets
| t |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
| x |
22 |
20 |
15 |
16 |
25 |
30 |
30 |
34 |
30 |
32 |
36 |
40 |
33 |
35 |
30 |
a) Make a control chart for the above data.
b) Determine whether the process is in statistical control. If it is not, specify which out-of-control signals are present.
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