#### description

- Mean , Median , Mode
- Quartile , Inter quartile

#### notes

The three measures of central tendency for ungrouped data are :

The **mean** (or average) of a number of observations is the sum of the values of all the observations divided by the total number of observations.

So, `bar x =

(sum_(i=1)^n x_i)/ n`.

For an ungrouped frequency distribution, it is `bar x = (sum_(i=1)^n f_ix_i)/(sum_(i=1)^n f_i)`

The **median** is that value of the given number of observations, which divides it into exactly two parts.

If n is an odd number, the median = value of the `((n + 1)/2)^(th)` observation.

If n is an even number, median = Mean of the values of the `(n/2)^(th)` and `(n/2 + 1)^(th)` observation.

The **mode** is that value of the observation which occurs most frequently, i.e., an observation with the maximum frequency is called the mode.