Question

Find the mean and variance for the data

$x_i$	6	10	14	18	24	28	30
$f_i$	2	4	7	12	8	4	3

Answer 1

Here $N=40,\sum _{i=1}^7{f}_i{x}_i=760$

$\therefore \overline{x}=\frac{\sum _{i=1}^7{f}_i{x}_i}{N}=\frac{760}{40}=19$

$Variance=(\sigma {)}^2=\frac{1}{N}\sum _{i=1}^7{f}_i{(x_i-\overline{x})}^2=\frac{1}{40}\times 1736=43.4$