Click on the following links. Please note these will open in a new window.

Using a frequency table to calculate central tendency and variability measures
https://www.youtube.com/watch?v=ZDneFcEVlNE
This video was created by Chieh-Chen Bowen.

Mean, Median and Mode 
https://www.youtube.com/watch?v=gYTwioS4mbo
Describes the differences amongst the three measures of central tendency, mean, median and mode. Also, depicts the computation of the three measures using ungrouped data.

https://www.youtube.com/watch?v=gMaIREesP7Y
Mean, mode and median from frequency tables

Weighted Mean
https://www.youtube.com/watch?v=Yl1aOD3CZbM
Shows the computation of weighted mean which means calculating the mean by taking into account the weight of each data point.

Standard Deviation
https://www.youtube.com/watch?v=qqOyy_NjflU
How to calculate Standard Deviation and Variance