 | |
|
| Module 3: Interpreting data
5.3 Scatter plots
5.3.1 Example of a scatter plot
The marketing manager of a large supermarket chain would like to determine the effect on sales of the amount of shelf space given to displaying pet foods. (Is the amount of space important, or will people buy it anyway?)
A random sample of 12 similar stores is selected from the chain, with the following results:
store | shelf space (X)
in feet | weekly sales (Y)
in $100's |
1 | 5 | 1.6 |
2 | 5 | 2.2 |
3 | 5 | 1.4 |
4 | 10 | 1.9 |
5 | 10 | 2.4 |
6 | 10 | 2.6 |
7 | 15 | 2.3 |
8 | 15 | 2.7 |
9 | 15 | 2.8 |
10 | 20 | 2.6 |
11 | 20 | 2.9 |
12 | 20 | 3.1 |
The scatterplot of the data follows:
There is a clear association between the variable "shelf space" and the variable "sales". Increasing shelf space produces increased sales. This association is made more clear by superimposing (drawing) a line on the plot to show the trend / direction of the data points.
| |
|
This page last updated 31 August 2009 | 
