MGT-455 Topic 4 Chapter 6 Problem Set Assignment

Chapter 6 Problem Set

Complete problems 6.12, S6.11, S6.20, S6.23, S6.27, and S6.41 in the textbook

Submit one Excel file.  Put each problem result on a separate sheet in your file.  Ensure that your last name is in your filename.

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Problem 6.12

Mary Beth Marrs, the Manager of an apartment complex, feels overwhelmed by the number of complaints she is reveiving. Below is the check sheet she has kept for the past 12 weeks. Develop a Pareto chart using this information. What recommendations would you make?

Problem S6.11

Twelve samples, each containing five parts, were taken from a process that produces steel rods at Emmanuel Kodzi’s factory. The length of each rod in the samples was determined. The results were tabulated and sample means and ranges were computed. The results were:

Sample Sample Mean (in.) Range (in.)
1 10.002 0.011
2 10.002 0.014
3 9.991 0.007
4 10.006 0.022
5 9.997 0.013
6 9.999 0.012
7 10.001 0.008
8 10.005 0.013
9 9.995 0.004
10 10.001 0.011
11 10.001 0.014
12 10.006 0.009

a) Determine the upper and lower control limits and the overall means for x- charts and R- charts.

b) Draw the charts and plot the values of the sample means and ranges.

c) Do the data indicate a process that is in control?

d) Why or why not?

Problem S6.20

Jamison Kovach Supply Company manufactures paper clips and other office products. Although inexpensive, paper clips have provided the firm with a high margin of profitability. Sample size is 200. Results are given for the last 10 samples.

SAMPLE 1 2 3 4 5 6 7 8 9 10
DEFECTIVES 5 7 4 4 6 3 5 6 2 8

a) Establish upper and lower control limits for the control chart and graph the data.

b) Has the process been in control?

c) If the sample size were 100 instead, how would your limits and conclusions change?

Problem S6.23

The school board is trying to evaluate a new math program introduced to second-graders in five elementary schools across the county this year. A sample of the student scores on standardized math tests in each elementary school yielded the following data:

School No. of test Errors
A 52
B 27
C 35
D 44
E 55

Construct a c-chart for test errors, and set the control limits to contain 99.73% of the random variation in test scores. What does the chart tell you? Has the new math program been effective?

Problem S6.27

One of New England Air’s top competitive priorities is on-time arrivals. Quality VP Clair Bond decided to personally monitor New England Air’s performance. Each week for the past 30 weeks, Bond checked a random sample of 100 flight arrivals for on-time performance. The table that follows contains the number of flights that did not meet New England Air’s definition of “on time”:

1 2 16 2
2 4 17 3
3 10 18 7
4 4 19 3
5 1 20 2
6 1 21 3
7 13 22 7
8 9 23 4
9 11 24 3
10 0 25 2
11 3 26 2
12 4 27 0
13 2 28 1
14 2 29 3
15 8 30 4

a) Using a 95% confidence level, plot the overall percentage of late flights (p) and the upper and lower control limits on a control chart.

b) Assume that the airline industry’s upper and lower control limits for flights that are not on time are .1000 and .0400, respectively. Draw them on your control chart.

c) Plot the percentage of late flights in each sample. Do all samples fall within New England Air’s control limits? When one falls outside the control limits, what should be done?

d) What can Clair Bond report about the quality of service?

Problem S6.41

Meena Chavan Corp.’s computer chip production process yields DRAM chips with an average life of 1,800 hours and s = 100 hours. The tolerance upper and lower specification limits are 2,400 hours and 1,600 hours, respectively. Is this process capable of producing DRAM chips to specification?

Course: MGT-455 Production/Operations Management
School: Grand Canyon University

  • 01/04/2020
  • 140
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