Chapter Contents |
Previous |
Next |
RCHART Statement |
The following notation is used in this section:
process standard deviation (standard deviation of the population of measurements) | |
Ri | range of measurements in i th subgroup |
ni | sample size of i th subgroup |
d2(n) | expected value of the range of n independent normally distributed variables with unit standard deviation |
d3(n) | standard error of the range of n independent observations from a normal population with unit standard deviation |
Dp(n) | 100p th percentile of the distribution of the range of n independent observations from a normal population with unit standard deviation |
The following table provides the formulas for the limits:
Table 39.21: Limits for R ChartsControl Limits |
LCL = lower limit |
UCL = upper limit = |
Probability Limits |
LCL = lower limit |
UCL = upper limit |
The formulas assume that the data are normally distributed. Note that the control limits vary with ni and that the probability limits for Ri are asymmetric around the central line. If a standard value is available for , replace with in Table 39.21.
You can specify parameters for the limits as follows:
Chapter Contents |
Previous |
Next |
Top |
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.