SQL - STDEVP 或 STDEV 以及如何使用它？

Question

我有一张 table :

LocationId OriginalValue Mean
1          0.45         3.99  
2          0.33         3.99
3          16.74        3.99
4          3.31         3.99

等等...

我如何使用此表计算出标准偏差？您会推荐什么 - STDEVP 或 STDEV？

Answer 1

要使用它，只需:

SELECT STDEVP(OriginalValue)
FROM yourTable

从下面开始，您可能需要 STDEVP。

来自here :

STDEV is used when the group of numbers being evaluated are only a partial sampling of the whole population. The denominator for dividing the sum of squared deviations is N-1, where N is the number of observations ( a count of items in the data set ). Technically, subtracting the 1 is referred to as "non-biased."

STDEVP is used when the group of numbers being evaluated is complete - it's the entire population of values. In this case, the 1 is NOT subtracted and the denominator for dividing the sum of squared deviations is simply N itself, the number of observations ( a count of items in the data set ). Technically, this is referred to as "biased." Remembering that the P in STDEVP stands for "population" may be helpful. Since the data set is not a mere sample, but constituted of ALL the actual values, this standard deviation function can return a more precise result.