Question

The marks obtained by seven students are 8, 9, 11, 13, 14, 15 and 21. Find the variance and standard deviation of these marks.

Answer 1

Here,

Mean, \(\bar{x}=\frac{8+9+11+13+14+15+21}{7}\)

= 13

Here,

N = 7, \(\sum(x_i-\bar{x})^2\)

∴ \(σ^2= \frac{1}{n}\sum (x_i-\bar{x})^2\)

\(= \frac{114}{7}\)

= 16.29

And,

\(σ=\sqrt{16.29}\)

= 4.04

∴ Variance = 16.29 and standard deviation = 4.04.