need a custom calculation script to calculate standard deviation

Question

need a custom calculation script to calculate standard deviation from 8 Rows , this will be a .pdf form the input variable data points will be from users using this template as a form.

I can get the average from the simple calculation but struggling with the script for the standard deviation. Any help would be appreciated.

Header 1	Header 2	Header 3	Header 4	Header 5	Header 6	Header 7	Header 8	Header 9	Header 11
sample1Row1	sample2Row1	sample3Row1	sample4Row1	sample5Row1	sample6Row1	sample7Row1	sample8Row1	Average	stddeviation

try67 · Accepted Answer

so if I take sample1Row1, sample2Row1,..... sample8Row1 = 1,2,3,4,5,6,7,8

the average would be 1+2+3+4+5+6+7+8 / 8 = 4.5

The desired output should be :

Stddev = sqrt {[summation [(x - 4.5)^2] / (8-1)} = sqrt { [sum [(1-4.5)^2 +.........+(8-4.5)^2] ] / (8-1)

= sqrt { [sum (12.25 + 6.25 + 2.25 + 0.25 + 0.25 +2.25 +6.25+12.25 )] / (8-1)}

= sqrt { 42/7}

= 6

So the formula is not:

stddev = sqrt (sum (sampleXRow1 - average)^2 / (n-1))

But:

stddev = sqrt (sum ((sampleXRow1 - average)^2) / (n-1))

So the code should be something like this:

var avg = Number(this.getField("AverageRow1").valueAsString); 
var sum = 0; 
var n = 0; 
for (var i=1; i<=8; i++) { 
    var v = this.getField("sample"+i+"Row1").valueAsString; 
    if (v!="") { 
        sum+=Math.pow((Number(v)-avg),2);
        n++; 
    } 
} 
if (n==0 || n==1) event.value = ""; 
else event.value = Math.sqrt(sum / (n-1));

try67 · Answer

What's the formula that you want to use?

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