Chapter Contents |
Previous |
Next |
XSCHART Statement |
See SHWXS2 in the SAS/QC Sample Library |
This example illustrates how to
create and s charts with probability limits.
The following statements read the kilowatt power output measurements
from the data set TURBINE (see
"Creating Charts for Means and Standard Deviations from Raw Data" ) and create
the and s charts shown in Output 44.1.1:
title 'Mean and Standard Deviation Charts With Probability Limits'; symbol v=dot c=salmon; proc shewhart data=turbine; xschart kwatts*day / alpha = 0.01 outlimits = oillim cframe = lib cinfill = bwh cconnect = salmon; run;
The ALPHA= option specifies the probability () that a
subgroup summary statistic is outside the limits.
Here, the limits are computed so that
the probability that a subgroup mean or
standard deviation is less than its lower limit is ,and the probability that a subgroup mean or standard deviation
is greater than its upper limit is . This assumes
that the measurements are normally distributed.
The OUTLIMITS= option names an output data set (OILSUM) that saves the probability limits. The data set OILLIM is shown in Output 44.1.2.
Output 44.1.1: Probability Limits on and s ChartsSince all the points fall within the probability limits, it can be concluded that the process is in statistical control.
Chapter Contents |
Previous |
Next |
Top |
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.