Measures of variation summarize the spread of a data set.

They describe how measurements differ from each other and/or from their mean.

Range

Interquartile range and

Standard deviation.

Standard deviation can be referred to be the degree of dispersion.

It describes the way in which the values are spread across the data sample and also it is the measure of the variation of the data points from the mean.

It is numerically the positive square root of ‘Variance’.

Depending on whether you have collected data from a whole population or a sample.

Where n = no. of observations

\$X_i\$ = value of samples

\$\barX\$ = mean of the samples (or) \$ \frac{ \sum_{i=0}^N X_i}{N} \$

Find the mean.

Find the deviation from the mean (or) the difference of each number from the mean.

square each devation from the mean.

Find the sum of the squares.

Find the variance (or) divide with no.of observations(N) for sample standard deviation and with no. of observations(n-1) for sample standard deviation.

Find the square root of the variance.

Standard deviation =\$\sqrt variance\$