| Scatter Plots and Best-Fitting Lines |
[Back] |
as x increases, y increases
In the graph below, the data
points show a correlation between an increase in study time and the score earned
on the test. How could a student use this information?
N.B. Best-Fitting
Lines shown in blue
A student could use this information to estimate a realistic amount of time required to study for a test.
as x increases, y decreases
In the graph below, the data points show a correlation between an the number of shoppers going to a mall versus daily rainfall amounts. How could a store manager use this information?
A store manager could use this information to schedule employees based on predicted rainfall.
x and y are independent of one another
In the graph below, there is no clear correlation (positive or negative) between a student's height and their performance on the mid-term exam. Therefore, no best-fitting line is drawn.
Best-Fitting Line - A line drawn so it is close to most or all of the data points in a graph. The technical aspect of fitting a line to data points is a field of study called "Regression Analysis." In this introductory lesson, we will simply draw the line as best as our eye can estimate.
A best-fitting line is described as strong or weak depending on how close the data points are on average.
In the examples above, the best-fitting line in the first example demonstrates a stronger correlation than the second example, since the data points (on average) are closer to the line.