I am trying to create an SPC control chart with moving averages. Unfortunately I don't seem to be able to calculate the first values correctly. I need the chart to do the following with the data column:
Iterate down the data
for each data point do the following:
- Calculate the mean and standard deviation for all the data points so far
- Calculate the number of data points that are above the mean+stdev
- Calculate the number of data points that are below the mean-stdev
- If either number of data points is 8 set the first mean value as the most recently calculated mean, stdev as most recently calculated stdev. Rinse, repeat all the way along the data set.
As far as I can see, Qlikview can't do this, however solutions involving doing this with the data during load seem to massively diminish the usefulness of Qlikview because either the data set gets huge or a limited number of user selections are available.
