Statistics - Comparing plots


Advertisements

Groups of population can be compared using box and whisker plots. Overall visible spread and difference between median is used to draw conclusion that there tends to be a difference between two groups or not.

Comparing plots

Case 2: Formula

${P = \frac{DBM}{OVS} \times 100 }$

Where −

  • ${P}$ = percentage difference

  • ${DBM}$ = Difference Between Medians.

  • ${OVS}$ = Overall Visible Spread.

Rules

  • For a sample size of 30 if this percentage is greater than 33% there tends to be a difference between two groups.

  • For a sample size of 100 if this percentage is greater than 20% there tends to be a difference between two groups.

  • For a sample size of 1000 if this percentage is greater than 10% there tends to be a difference between two groups.

Example

Problem Statement:

Describe the difference between following sets of data.

Sr. No.NameSet ASet B
1Max1215
2UQ1013
3Median710
4LQ69
5Min56

Solution:

Consider the following diagram:

Comparing plots

${OVS = 13 - 6 \\[7pt] \ = 7 \\[7pt] \ DBM = 10 -3 \\[7pt] \ = 4 }$

Apply the formula

${P = \frac{DBM}{OVS} \times 100 \\[7pt] \ = \frac{4}{7} \times 100 \\[7pt] \ = 57.14 }$

As percentage is over 33% thus there is difference between Set A and Set B. It is likely that Set B is greater than Set A.

Advertisements