Measures of Dispersion (Variance & Standard Deviation)

Note: Find µ first 

Keys:

Ungrouped data

S = Summation Notation (sum of…)

c = the value of the data set

µ = the mean of the data set

n = the number of data points 

Grouped data

S = Summation Notation (sum of…)

fi = Frequency

mi = Midpoint

µ = the mean of data set

n = Sum of frequency

Example 1 (Ungrouped data)

The Maths test scores of five students are: 92, 88, 80, 68 and 52. Find the variance and standard Deviation.

Example 2 (Grouped data)

Find the Variance and Standard Deviation.

Retrieve from Sir Rodelin and Sir Habir (2015-2016). Lecturer of Cosmopolitan College of Commerce & Technology