Quality Quiz from Professor Cleary
"B" is the correct answer!
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In fact, this process is out of control. What the
dynamic duo failed to take into account is the fact that the 's
in a process that is in control will form a normal distribution,
Viewing the area under a normal curve and moving plus and minus one standard error will capture about 64 percent of the data; plus or minus two standard errors, 95 percent; and plus or minus three standard errors, 99.7 percent.
Returning to the chart produced by
Phillip D. Tank, one can see that 100 percent of the X-bars ('s)
are within plus and minus one standard error. This may appear to
be positive, but in fact it is statistically impossible to achieve.
It may be that Phillip has deliberately
altered the data or tampered with the process itself. This is known
as the "too good to be true" outcome. It may be that in
his earnest effort to unseat Marsha and Maura, he has used a magic
pencil to record data.
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