MEASURE OF DISPERSION PART 1

OBJECTIVES 

1. The definition of Measure of Dispersion 

2. Finding Range

3. The use of Interquartile range 

What is Measure of Dispersion? 

Measure of Dispersion are used examine the spread of data. 

Types of methods that are used: 

1. Range 

2. Quartiles

Range

What is range? From the word itself it means the area of variation between upper and lower limits on a particular scale. In this case, to find range, the largest value are been minus with the smallest value in data set. 

Range = x (max value) - x (min value) 

Example 

4, 7, 3, 8, 9

9 - 3 = 6 

Quartiles 

What is mean by quartiles? In statistics, quartile is each of four equal groups into which a population can be divided according to the distribution of values of a particular variable. From the word itselfs, QUARtile, Quar means four.

example 1:

Write down the range, upper quartile and lower quartile for the following numbers:

Data : 2, 4, 6, 10, 13, 15

range = highest - lowest 

= 15 - 2

Range = 13

median = (10+6)/2 = 8

lower quartile = 4

upper quartile = 13

example 2 : 

Find the lower quartile, middle quartile and upper quartile for the following numbers:

Data : 1, 3, 3, 4, 5, 6, 6, 7, 8, 8 

Lower quartile : 3

Middle quartile : 5.5 

Upper quartile : 7 

example 3 : 

Find the range in between 4, 6, 9, 3, 7 

Range = highest - lowest 

= 9 - 3

= 6