Provides description and example of how to calculate standard deviation.

 

An online simulation illustrates how changes in the mean and standard deviation affect the position and shape of the distribution.

 

This article describes interquartile range including what it is, how to find it, what it is used for, and its history. Also includes a video on the website that calculates an example.

 

This article provides a more in-depth explanation why the sample variance has n-1 in the denominator.