Friday 11 November 2011
Tuesday 8 November 2011
Run Chart Rules! - What you need to know about run charts...
Run chart can be used to detect any nonrandom process behavior. Data for run chart is plotted sequentially with a reference line called median. In Minitab, Run chart can detect oscillation, clustering, mixtures and trends by the two tests for nonrandom behavior.
There are four rules you can apply to validate if an improvement is the endresult of any changes you made to the process.
Rule one: shift.
This rule is in force when there are six or more consecutive points either all above or all below the median. Skip values that fall on the median because value that fall on the median neither add to nor break a shift.
Rule two: trend.
This rule is in force when there are five or more consecutive points all going up or all going down. When using this role, ensure that you are not counting points which as same values.
Rule three: number of runs.
This rule is in force when there are too few or too many runs. Determine the
number of runs by counting the number of times the line connecting the data
points crosses the median and add one.
Rule four: astronomical point.
These are the data points which are unusually high or low in value compare to other values. Don't get confused with the regular high and low end of the run chart points.
There are four rules you can apply to validate if an improvement is the endresult of any changes you made to the process.
Rule one: shift.
This rule is in force when there are six or more consecutive points either all above or all below the median. Skip values that fall on the median because value that fall on the median neither add to nor break a shift.
Rule two: trend.
This rule is in force when there are five or more consecutive points all going up or all going down. When using this role, ensure that you are not counting points which as same values.
Rule three: number of runs.
This rule is in force when there are too few or too many runs. Determine the
number of runs by counting the number of times the line connecting the data
points crosses the median and add one.
Rule four: astronomical point.
These are the data points which are unusually high or low in value compare to other values. Don't get confused with the regular high and low end of the run chart points.
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