It looks like you are using Shewhart rules for this. I've never seen Excel
used to determine if any of the tests fail. I've used other software
packages for it. I'm sure someone else can answer your question, I'm
wondering if you'd want to see if the rule failed for the last n points, or
do you want the chart to display every time the rule fails.

Jon Peltier's Dynamic control chart may help you.

http://www.peltiertech.com/Excel/Cha...s.html#CtrlCht

1. 7 points or more in a row on one side (above or below) the average
2. 7 points in a row that are constantly decreasing no matter where they
fall in
relation to the average.
3. 7 points in a row that are constantly increasing no matter where they
fall in
relation to the average.
4. Do 2/3rds of the points lie within the middle 1/3rd of the graph

"Neil" wrote:

Does anyone know of a method for analysing points on a line chart that I have
created?

I have a chart with 30point on its, and a line plotted along the middle
which is the average of the 30 readings.

I have to use the following rules to check the chart, looking for the
following conditions.

1. 7 points or more in a row on one side (above or below) the average
2. 7 points in a row that are constantly decreasing no matter where they
fall in
relation to the average.
3. 7 points in a row that are constantly increasing no matter where they
fall in
relation to the average.
4. Do 2/3rds of the points lie within the middle 1/3rd of the graph

I'm not sure if any of this can be re-created automatically maybe using VBA?
But if anyone has any suggestions as to how I can automate this analysis, so
that I can give the Workbook to unskilled operators and let it tell them when
one of the rules is broken, then your suggestions will be very welcome

Thanks in advance

Ian