Stats
P control chart, answers to on your own exercises (March 7, 2007)
Category: Control charts
On the web page
you were asked to calculate P charts for the following two data sets:
Worker #2:
60 56 78 60 74 70 70 68 82 76 72 76
68 78 76 68 74 56 74 62 60 70 60 84
Worker #3:
24 32 20 14 32 22 20 26 26 38 30 16
36 32 38 14 26 14 38 20 14 18 22 34
For worker #2, the average of all 24 proportions is 0.6967. The control
limits are calculated as
and the control chart is
Notice that the computer rounds these numbers slightly differently,
reporting the lower control limit as 0.50 rather than 0.51. Do not worry
about these small differences, but the computer's value is slightly more
accurate.
There are no points out of control on this chart.
For worker #3, the average proportion is 0.2525. The control limits are
calculated as
and the control chart is
Again, the answers diverge slightly because of rounding. There are no
points out of control on this chart.
07/08/2008.
