Data Analysis - Teach.sg

Measures of Central Tendency

Measure	Definition
Mean	$\dfrac{\text{sum of all numbers}}{\text{number of numbers}}$
Median	Middle value when data is ordered
Mode	Most frequent value

Measure	Formula
Range	Maximum $-$ Minimum
Interquartile Range	$Q_3 - Q_1$

Ungrouped Data:

Mean

$\bar{x} = \dfrac{\sum x}{n}$

Standard Deviation

$\sigma = \sqrt{\dfrac{\sum(x-\bar{x})^2}{n}}$

Grouped Data:

Mean

$\bar{x} = \dfrac{\sum fx}{\sum f}$

Standard Deviation

$\sigma = \sqrt{\dfrac{\sum fx^2}{\sum f} - \left(\dfrac{\sum fx}{\sum f}\right)^2}$