The time (in seconds) taken by a group of people to walk across a pedestrian crossing is given in the table below.

Calculate the variance and standard deviation of the data.

The number of books bought at a book fair by 200 students from a school are given in the following table.

Calculate the standard deviation.

Calculate the variance of the following data

A group of 45 house owners contributed money towards green environment of their street. The amount of money collected is shown in the table below.

Calculate the variance and standard deviation.

Find the variance of the following distribution.