18th May Learning Summary of Statistics

Today Sal introduced concepts, Population and Sample.

And their Variance and Stanard Deviation

图片发自App

But the difference between population and sample is that when you calculate the variance and standard deviation, you have to minus 1 more on "n" which is numbers of the sample.

Sal didn't explain a lot on this, but it's ok, I think I will learn that sooner or later.