A control chart is a line chart of the data, with extra lines showing
control limits. Your data looks like this:
Errors
Monday 2
Tuesday 10
Wednesday 4
Select the data, including the blank cell at the top left, and make a
Line Chart with the Chart Wizard (button on the command bar, or Insert
menu > Chart).
The lines in a control chart could include Mean, Upper and Lower Spec
Limits, and Upper and Lower Control Limits. Given the small sample, your
Mean is 5.333 and the StDev is 4.163. Control limits are usually given
as the Mean ± 3 StDevs. Three StDevs below the mean is meaningless, so
the Lower Control Limit is 0 (zero). Three StDevs above the mean, the
Upper Control Limit, is 17.823, while the Upper Spec Limit is the
allowed 20 errors.
I suspect there is more than three days of data that should be used to
determine your control limits.
You can use one of the techniques on my web site for adding a horizontal
line to your chart:
http://peltiertech.com/Excel/Charts/AddLine.html
- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
http://PeltierTech.com/Excel/Charts/
_______
mchcullinane < wrote:
> I need to create a control chart. I have no idea how to do this.
>
> I'm looking to create a chart that can distinguish between variations
> in a process due to common causes and variations de to special causes.
> I need to show an upper control line, a control line and a lower
> control line. And then show where my data is between these lines. ex.
> say I am aloud a max. of 20 keying errors and the standard min is 2. On
> monday I make two erros, on tues I make 10 and on wednesday 4. I need
> to chart these differences and show lines for the min. avg. and max.
>
>
> ---
> Message posted from http://www.ExcelForum.com/
>
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