If the range is zero SD will be zero. Why?
When can range be zero?
When set is one element set or all the elements of set is identical.
In either case mean of the set will be the number in the set.
What is SD?
It is the dispersion of individual element of set from mean. Now if the mean is that same identical number of set, there is no dispersion. Hence SD will be zero.Posted from my mobile device
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