What is the difference between low and high variance?

Question

Thank you in advance.

Answer 1

Variance is defined as V = (sum of squares of individual values - square of average of those values)/Number of individual values

Larger variance or high variance means the individual values are spread out around the average and may mean poor process control. Low variance means the values are closer to the average and that means better process control.

Let us take an example: 3, 6 and 9 have higher variance than 5, 6 and 7 though the average in both cases is same, i.e 6. If 3, 6 and 9 represent the heights of an animal species, we can safely say that we are not talking of humans (though 3 and 6 are probable, 9 ft. is quite unlikely). 5, 6 and 7 feet are, on the other hand, probably representative of human poulation (7 is less frequent but if we do a little rounding off we can approach 7, in any case, the probability of finding a man of 7 ft. height is much more than finding a man of 9 ft. height).

Pl. see http://davidmlane.com/hyperstat/A16252.html for formulas etc.

Answer 2

Low Variance