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.
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
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
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