X Median R Chart Formulas
QI Macros can calculate them for you!
Create an XmedianR Chart using QI Macros
- Select your data.
- Select XmedianR on QI Macros menu.
- QI Macros will do the math and draw the graph for you.
Go Deeper:
The XMedianR Chart works just like the XbarR chart except that it uses the median instead of the average as a measure of central tendency.
XMedianR Chart formulas for the Range and Median charts.
Range Chart Formula
X Median Chart Formula
n = number of samples in a subgroup
k = number of subgroups used to determine the average median and range
Conforms with AIAG SPC 2nd Edition
NOTE: It is possible to have negative limits on an XMedianR Chart.
Process: Calculate, plot, and evaluate the range chart first. If it is "out of control," so is the process. If the range chart looks okay, then calculate, plot, and evaluate the X Chart.
Note: There are no known calculations for constants in an XMedianR Chart where n > 100
The XMedianR Chart is just one of the tools included in QI Macros SPC Software for Excel.
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