MULTIPLE CHOICE
1.If x = 23 ounces, σ = 0.4 ounces, and n = 16, the ±3σ control limits will be
1.a. 21.8 to 24.2 ounces
2.b. 23 ounces
3.c. 22.70 to 23.30 ounces
4.d. 22.25 to 23.75 ounces
5.e. none of the above
2.The usual purpose of an R-chart is to signal whether there has been a
1.a. gain or loss in dispersion
2.b. change in the percent defective in a sample
3.c. change in the central tendency of the process output
4.d. change in the number of defects in a sample
5.e. none of the above
3.A manager wishes to build a 3σ range chart for a process. The sample size is five, the mean of sample means is 16.01, and the average range is 5.3. From Table S6.1, the appropriate value of D3 is 0, and D4 is 2.115. The UCL and LCL for this range chart are
1.a. 33.9 and 11.2
2.b. 33.9 and 0
3.c. 11.2 and 0
4. d. 6.3 and 0
5.e. 31.91 and 0.11
4.Plots of sample ranges indicate that the most recent value is below the lower control limit. What course of action would you recommend?
1.a. Since there is no obvious pattern in the measurements, variability is in control.
2.b. One value outside the control limits is insufficient to warrant any action.
3.c. Lower than expected dispersion is a desirable condition; there is no reason to investigate.
4.d. The process is out of control; reject the last units produced.
5.e. Variation is not in control; investigate what created this condition.
5.To set x-chart upper and lower control limits, one must know the process central line, which is the
1.a. average of the sample means
2.b. total number of defects in the population
3.c. percent defects in the population
4.d. size of the population
5. e. average range
6.According to the text, the most common choice of limits for control charts is usually
1.a. ± 1 standard deviation
2.b. ± 2 standard deviations
3.c. ± 3 standard deviations
4.d. ± 3 standard deviations for means and ± 2 standard deviations for ranges
5.e. none of the above
7.Which of the following is true of a p-chart?
1.a. The lower control limit is found by subtracting a fraction from the average number of defects.
2.b. The lower control limit indicates the minimum acceptable number of defects.
3.c. The lower control limit may be below zero.
4.d. The lower control limit may be at zero.
5.e. The lower control limit is the same as the lot tolerance percent defective.
8.The normal application of a p-chart is in
1.a. process sampling by variables
2.b. acceptance sampling by variables
3.c. process sampling by attributes
4.d. acceptance sampling by attributes
5.e. none of the above
9.The statistical process chart used to control the number of defects per unit of output is the
1.a. x-chart
2.b. R-chart
3. c. p-chart
4.d. AOQ chart
5. e c-chart
10.The c-chart signals whether there has been a
1.a. gain or loss in uniformity
2.b. change in the number of defects per unit
3.c. change in the central tendency of the process output
4.d. change in the percent defective in a sample
5.e. change in the AOQ
11.The local newspaper receives several complaints per day about typographic errors. Over a seven-day period, the publisher has received calls from readers reporting the following number of errors: 4, 3, 2, 6, 7, 3, and 9. Based on these data alone, what type of control chart(s) should the publisher use?
1. a. p-chart
2.b. c-chart
3. c. x-chart
4.d. R-chart
5. e. x-and R-charts
12.A manufacturer uses statistical process control to control the quality of the firm's products. Samples of 50 of Product A are taken, and a defective/acceptable decision is made on each unit sampled. For Product B, the number of flaws per unit is counted. What type(s) of control charts should be used?
1.a. p-charts for A and B
2.b. p-chart for A, c-chart for B
3.c. c-charts for both A and B
4.d. p-chart for A, mean and range charts for B
5.e. c-chart for A, mean and range charts for B
13.A nationwide parcel delivery service keeps track of the number of late deliveries (more than 30 minutes past the time promised to clients) per day. They plan on using a control chart to plot their results. Which type of control chart(s) would you recommend?
1.a. x-and R-charts
2.b. p-charts
3.c. c-charts
4.d. x-, but not R-charts
5.e. both p- and c-charts
14.A run test is used
1.a. to examine variability in acceptance sampling plans
2.b. in acceptance sampling to establish control
3.c. to examine points in a control chart to check for natural variability
4.d. to examine points in a control chart to check for nonrandom variability
5.e. none of the above
15.Which of the following is true regarding the process capability index Cpk?
1.a. A Cpk index value of 1 is ideal, meaning all units meet specifications.
2.b. The larger the Cpk, the more units meet specifications.
3.c. The Cpk index can only be used when the process centerline is also the specification centerline.
4.d. Positive values of the Cpk index are good; negative values are bad.
5.e. None of the above is true.
16.If the Cpk index exceeds 1
1.a.the AQL must be smaller than the LTPD
2.b.σ must be less than one-third of the difference between the specification and the process mean
3.c.the x-bar chart must indicate that the process is in control
4.d.the process is capable of Six Sigma quality
5.e.the process is characterized as "not capable"
17.The statistical definition of Six Sigma allows for 3.4 defects per million. This is achieved by a Cpk index of
1.a. 0
2.b.1
3.c.1.33
4. d.1.67
5. e.2
18.A Cpk index of 1.00 equates to a defect rate of
1.a. five percent
2.b. 3.4 defects per million
3.c. 2.7 per 1,000 items
4. d.97.23 percent
5.e. one percent