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talvin singh January 20th, 2017 02:39 AM

Skewed Deviation
 
Hi All,

Hope you're all well.

in excel, I am using 2 input parameters; average and standard deviation, and generating a set of 1000 lines using the random function. currently i have to avg set to 4.5 and stdev at 2.

=NORM.INV(RAND(),4.5,2)

i produce a graph and you can see a normal distribution curve. if i use the average function for the 1000 random numbers, it results around the 4.5 mark.

if i lower the avg to 1.3 for example, and keep stdev at 2, the graph goes into negative as expected and avg is around 1.3, but if i calculate the average for anything greater than zero, its never at 1.3.

I will never have a person buying less than zero items. therefore i require a skewed formula where the spread always starts from 1, where i input an average and stdev and create a sample of 1000 lines, and the average of the sample will always be around the input parameter set.

I there such a formula? I've tried forcing the less than zero to have 1, but that gives incorrect results =MAX(1,NORM.INV(RAND(),1.3,2))

Many thanks in advanced.


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