Consider the following questions:
1. Which of the following situations suggest a process that appears to be operating in a state of statistical control?
a. A control chart with a series of consecutive points that are above the center line and a series of consecutive points that are below the center line.
b. A control chart in which no points fall outside either the upper control limit or the lower control limit and no patterns are present.
c. A control chart in which several points fall outside the upper control limit.
d. All of the above.
2. A quality control analyst for a light bulb manufacturer is concerned that the time it takes to produce a batch of light bulbs is too erratic. Accordingly, the analyst randomly surveys 10 production periods each day for 14 days and records the sample mean and range for each day.
|
Day
|
X (in minutes)
|
R
|
|
1
|
58.5
|
5.1
|
|
2
|
47.6
|
7.8
|
|
3
|
64.3
|
6.1
|
|
4
|
60.6
|
5.7
|
|
5
|
63.7
|
6.2
|
|
6
|
57.5
|
6.0
|
|
7
|
55.0
|
5.4
|
|
8
|
54.9
|
6.1
|
|
9
|
55.0
|
5.9
|
|
10
|
62.7
|
5.0
|
|
11
|
61.9
|
7.1
|
|
12
|
60.0
|
6.5
|
|
13
|
58.3
|
5.9
|
|
14
|
52.0
|
5.2
|
Referring to the table, suppose the analyst constructs an R chart to see if the variability in production times is a control. What is the lower control limit for this R chart?
a. 4.84
b. 3.37
c. 2.98
d. 1.34
3. A political pollster randomly selects a sample of 100 voters each day for 8 successive days and asks how many will vote for the incumbent. The pollster wishes to construct a p chart to see if the percentage favoring the incumbent candidate is too erratic.
|
Sample (Day)
|
Number Favoring Incumbent
|
|
1
|
57
|
|
2
|
57
|
|
3
|
53
|
|
4
|
51
|
|
5
|
55
|
|
6
|
60
|
|
7
|
56
|
|
8
|
59
|
Referring to the table, what is the numerical value of the upper control limit for the p chart?