# What does it mean for a sample to have a standard deviation of zero? Describe the scores in such a sample?

What does it mean for a sample to have a standard deviation of zero? Describe the scores in such a sample?
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hajavaF
Given that sample standard deviation is Zero. this indicates that the variance of Sample is also Zero as square of sample standard deviation is Sample Variance.
Variance is average of the squared deviations from mean. As shown in below formula
Since Variance = 0 , we substitute in formula and we get the sum of squares of deviations of all data points from mean should be zero. This is only possible if and only if all the data points in the data distribution are same as mean of the data distribution. In this case the variance and standard deviaiton will be zero.
Variance $=\sum _{i=1}^{n}\frac{{\left({X}_{I}-\stackrel{―}{X}\right)}^{2}}{n-1}$
$0=\sum _{i=1}^{n}\frac{{\left({X}_{I}-\stackrel{―}{X}\right)}^{2}}{n-1}$
$\sum _{i=1}^{n}{\left({X}_{I}-\stackrel{―}{X}\right)}^{2}=0$