The Control Chart for Ranges compared with Bartletts Test

Thus B/C = 9.319/1.183 = 7.87 and is distributed as y/ with (k— 1) = 9 degrees of freedom. This is much less significant than the 10% level of significance, so there is no reason to suppose that the batches differ from each other in their internal variability. 

The use of Bartlett s Test thus leads to the same conclusion as the control chart for ranges. It requires more calculation, but on the other hand has the advantages of being more sensitive and precise. 

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