(PECL stats >= 1.0.0)
stats_variance — Returns the population variance
$a
[, bool $sample = false
] )本函数还未编写文档，仅有参数列表。
a
sample
Anonymous (2009-02-27 13:43:58)
This will return surprising values for most users, since the default of sample=false is rather unusual when speaking about variance.
Point is:
When using stats_variance($foo,TRUE) the sum is divided by n-1 while the default just divides it by n. So when you expect your variance to be lower you probable wanted to divide by n-1, therefore should set the second parameter =TRUE.