Here's September's question from
Professor Cleary. After you have read the question, click on the
response that you think is correct. If you answer correctly, you can
register to win a free copy of Quality Gamebox.
Dick Moby, quality assurance czar for a plastics extrusion company
somewhere in the Midwest, is serious about control charts. He sees data
analysis and process control as ways not only to assure high quality
products for his firm, but also to enhance his own career. He personally
instructs each new employee in his department, giving them a solid
foundation in the fundamentals of SPC. He has given the same attention
to Wanda Ring, who also aspires to advancement in the organization, and
has emphasized the importance of keeping all process data points between
the upper and lower control charts.
Wanda Ring is assigned to monitor a series of machines that extrude raw
materials used for manufacturing parts for toys. One of these machines,
she believes, is not operating with the same consistency that others on
the line demonstrate. Since she had some fleeting experience as an
operator prior to being hired by Dick Moby, she feels confident that by
adjusting the operation of the machine she can reduce the variability of
the process. The operator advises her not to tamper with the machine,
since this can contribute to variability in the process, but she says
that she knows what she's doing.
Wanda is using an individuals moving average chart. She decides to adopt
a decision rule: if a point falls above X-bar, she will adjust the
operation of the machine downward to compensate for the distance between
the data point and X-bar. If a data point falls below X-bar, on the
other hand, she would adjust the operation upward to compensate.
If Wanda follows this decision rule, which of the following will be
A) Variability of the
process will decrease by 50 percent;
B) Variability of the
process will increase by 100 percent;
C) Variability will
remain the same;
D) Variability will
increase by 25 percent.
Click on the correct answer, and link to