From Crash Course Statistics. This video will discuss "those numbers that tend to hang out in the middle of our data - the mean, the median, and mode." (11 m, 22 s)
The Organic Chemistry Tutor explains how to calculate the standard deviation using two examples. First step: calculate the sample standard mean before you calculate the sample standard deviation.
From VCE Further Maths tutorials. Core (Data Analysis) Tutorial. This video will show you how the "r" value works and how to estimate an "r" value from a scatterplot. (13 m, 1 s)