Measures of Dispersion (Range, Quartile and Box & whisker plot)

Measures of Dispersion

•          Used to quantity the spread of the data
•          The measures of dispersion are:

1.       Range

2.       Quartile

3.       Box & Whisker

4.       Variance

5.       Standard Deviation

Range?

Range is the difference between the highest and lowest.

Example 1

76, 45, 83, 68, 63. Find the Range.

Example 2

39, 19, 9, 29, 49, 59, 49. Find the Range.

Quartiles, Interquartile range and Semi Interquartile range

•        Quartiles is the spread of a data set by breaking the data set into quarters which we have to find first quartile (Q1), second quartile (Q2) and third quartile (Q3).
•          Interquartile range is the difference between the highest quartile (Q3) and the lowest quartile (Q1).
•         Semi Interquartile range is the half of Interquartile range.

Note: arrange the data set from lowest number to highest number.

Example 1

4, 10, 6, 1, 15, 3, 2, 1, 8. Find the; 1. Quartiles

                                                        2. Interquartile range

                                                        3. Semi Interquartile range

                                                         4. Construct a Box & whisker plot

References:

Lund Research Ltd.(2013) Laerd statistics. https://statistics.laerd.com/statistical-guides/measures-of-spread-standard-deviation.php

Retrieve from Sir Habir, Mathematics lecturer, (2016)