A populations is a collections of persons

A population is a collection of persons, objects or items of interest.

A sample is a portion of the whole and, if properly taken, is representative of the whole.

The population mean is represented by the Greek letter mu . It is given by the formula

The capital Greek letter sigma is commonly used in mathematics to represent a summation of all the numbers in a grouping.

N is the number of terms in the population.

The sample mean is represented by  .  It is given by the formula

n is the number of terms in the sample.

Median from Frequency Tables

In a frequency table, the observations are already arranged in an ascending order. We can obtain the median by looking for the value in the middle position.

Case 1. When the number of observations is odd, then the median is the value at the position.

Example:

The following is a frequency table of the score obtained in a mathematics quiz. Find the median score.