Posted: September 10th, 2022

QUALITY MANAGEMENT EM 632 – SECTION 50

QUALITY MANAGEMENT
EM 632 – SECTION 50
Week 3 Assignment
(selected or modified problems from text)
Quantitative:
See the Data Sets for Week 3 file in Excel for problem data. Use Minitab for all problems except for
Problem #2a, which should be completed using Excel (use Minitab for the rest of #2).
1) Sample data is collected for a critical dimension and samples consist of subgroups of five
measurements each. See data presented in #1 tab of the Excel file.
a) Set up x-bar and R control charts with the first 20 samples. Is the process in statistical control?
b) 10 new samples are collected. Plot the x-bar and R values on the control chart you
established in part (a) and draw conclusions about dimension size and variation.
2) The waiting time for treatment in a “minute-clinic” located in a drugstore is monitored using control
charts for individuals and the moving range. Data is captured for 30 successive measurements of waiting
time. Use Minitab except for part (a). See data presented in #2 tab of the Excel file.
a) Use Excel to calculate the individual and moving range control chart parameters using this
data. For the individual values chart parameters, use Equation (6.33) with n = 2. For the moving
range chart, use Equation (6.5) with R-bar equal to the mean of the MR values. Hint: See
Example 6.5 and do not worry if the LCL of the individual values chart is negative.
b) Construct individual and moving range control charts with the data provided and interpret
the results. Does the process appear to be in statistical control?
c) Plot the data on a normal probability plot. Is it reasonable to assume normality for waiting
time data? Wouldn’t a variable like waiting time often tend to have a distribution with a long tail
(skewed) to the right? Why?
d) Plot the data on a lognormal probability plot. Does the data fit a lognormal distribution?
e) Convert the data using lognormal transformation and construct individual and moving range
charts with the transformed data. Does the process appear to be in statistical control now?
3) The number of nonconforming switches in samples of size 150 are captured. See data presented in #3
tab of the Excel file and construct an NP chart for these data. Does the process appear to be in control?
4) The data provided in the #4 tab of the Excel file represent the results of inspecting all units of a
personal computer model produced for the past ten days. Does the process appear to be in control?
Hint: Be careful to select the correct type of control chart when answering this question.
5) Surface defects have been counted on 25 rectangular steel plates. Set up a control chart for
nonconformities using the data collected. See data presented in #5 tab of the Excel file and assume the
subgroup size is constant at 100 for each plate inspected. Does the data appear to be in control?
6) A paper mill uses a control chart to monitor the number of imperfections found in finished rolls of
paper. Production output is inspected for 20 days. Use the data captured in the #6 tab of the Excel file to
set up a control chart for nonconformities per roll of paper. Does the process appear to be in control?

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