Mean deviation from mean, class nine

Standard deviation class ten, using direct method

Quartile deviation class ten, optional mathematics

Questions for practice 

Mean deviation from median for individual series

Standard deviation class nine, optional mathematics

Calculate standard deviation of the given data
i. 5,7,12,15,19,21    Ans . 5.84
ii. 12,14,16,18,22,26    Ans . 4.76

Standard deviation class nine