NavList:

Marcel wrote: "The two standard deviation functions on the calculator or in the spread sheet are only correct if the population of measured data (and the infinite number of data they belong to) are normal distributed".

I do not agree with that statement. I think the formula for (an estimated) standard deviation can be used on any distribution. You can test this by randomly generating a sufficient number of samples of e.g. a uniform distribution, calculate the standard deviation and compare with the theoretical value, in this case distribution width divided by the square root of 12.

But the probabilities often referred to, e.g. 95% of the observations are within plus/minus 1.96 standard deviations, are applicable to normal distributions only.

Lars 59N 18E
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