Mean is the ratio of sum of all observations divided by number of observations.

Mean = (Sum of observations)/(number of observations)

### Mean of tabulated data

Let the frequencies of n observations x

_{1}, x

_{2}, x

_{3}, x

_{4},..., x

_{n} be f

_{1}, f

_{2}, f

_{3}, f

_{4},...,f

_{n} respectively. Then, we define mean to be,

Mean = (f_{1}x_{1} + f_{2}x_{2} + f_{3}x_{3} + f_{4}x_{4} + ... + f_{n}x_{n})/(f_{1} + f_{2} + f_{3} + f_{4} + ... + f_{n} = ∑(f·x)/∑f

where ∑ is Greek letter showing summation.

### Mean of grouped data

In a class interval, we take x as the value of the class mark and use the formula

Mean = ∑(f·x)/∑f

The observation which occurs maximum number of times is called the mode of the data. In a tabulated data the observation with maximum frequency is the mode.