Scatter Plots

An easy way to examine the data given is by scatter plot. When we plot the points from the given set of data onto a rectangular coordinate system, we have a scatter plot..

Let's look at the two examples.

Example 1: A cost modeller wants to know the likely cost of a new contract based on the data collected from previous contracts.

Estimated cost of previous contracts

Number of employees	Total cost of contract
10	$500,000
20	$700,000
8	$400,000
15	$600,000
2	$300,000

A scatter plot below uses the above data with the number of employees on the Y-axis and total cost of contract on the X-axis.

Scatter Plot of the Cost

Example 2: Suppose we wanted to predict a student's grade on a freshman college calculus midterm based on his/her SAT score.

SAT Scores and Calculus Midterm Scores of 10 former students

Student	SAT Score x	Calculus Midterm Score y
1	1100	89
2	1300	92
3	1000	86
4	1100	92
5	1200	90
6	1200	93
7	1400	98
8	1300	95
9	1000	88
10	1400	95

A scatter plot below uses the above data with the calculus midterm score on the Y-axis and SAT score on the X-axis.

Scatter Plot of the Test scores

We can see that the scatter plots can be useful to find any relationship that may exist among the data. Also, the scatter plots are helpful in analyzing the data and the errors in the linear regression analysis can be found easily.