Unlike Stem-and-leaf charts, histograms, and frequency distributions which are snapshots of process variation and tell you nothing about the source of variation, the multivari tool shows you variation (the enemy!!!) by separating it into three possible sources (within-piece, piece-to-piece, and time-to-time.)
If you wanted to determine whether the source of variation is due to within-piece, piece-to-piece, or time-to-time, you would use a multi-vari chart.
If you wanted to determine whether the source of variation is due to positional, temporal, or cyclical, you would use a multi-vari chart.
Generate Clues with Multi-vari Charts: this technique is especially well suited for analyzing multiple sources of common-cause variation: within piece, piece to piece, time to time, and process stream to process stream – (by Reducing Process Variation- Davis Bothe)
- Time is on the horizontal scale
- Variable measurement on the vertical scale
- shows most of the values
- assists in the breakdown of components of variation
- Unlike other charts, Mulit vari will show all measurements recorded.
- Ex. Front, back, left & right thickness of a sheet of metal.
Also see Scatter Diagrams, Charts, Analysis
Six Sigma Black Belt Certification Multi-vari Questions:
Question: Positional, cyclical, and temporal variations are most commonly analyzed in: Taken from (ASQ sample Black Belt exam.)
Answer: (B) Multi-vari charts. SPC or statistical process control (including run charts) help you monitor how an on-going process is performing., so options A and D are not correct. Cause and effect diagrams are concerned with root cause analysis, so option C is not correct.