Summation for Statistical Control Chart on Excel

[anuneabreu]

How can I do the following formulas on excel... I have a a respective column with values for each of my variables they are all changing. M changes incrementally by 1 and ni and si change with no particular pattern. Thank you ahead of time!

 

[Kaper]

Is the number of rows with data steady?
(you mentioned m changes by one, but it's i which changes while m is the upper bound for the i variable)

Let's assume it is and your data are always in rows 2:10
Let's assume:
ni is listed in column B,
xi in column C
si in column D
first formula would be:

=sumproduct(B2:B10,C2:C10)/SUM(B2:B10)

The second one

=(sumproduct((B2:B10-1);D2:D10^2)/(SUM(B2:B10)-9))^0.5

If m isn't constant, probably easiest way is to extend bottom ranges to larger row number than expected maximum number of rows with data
For instance with the second formula being

=(sumproduct((B2:B100-1);D2:D100^2)/(SUM(B2:B100)-COUNT(B2:B100)))^0.5