A line of best fit (or "trend" line) is a straight line that best represents the data on a scatter plot. This line may pass through some of the points, none of the points, or all of the points. However, it always represents the general trend of the of the points, so we can determine whether there is a positive, negative or no relationship. Lines of best fit are really handy as they help us determine whether there is a relationship between two variables, which we can use to make predictions.
To draw a line of best fit, balance the number of points above the line with the number of points below the line.
Examples
Question 1
The following scatter plot shows the data for two variables, $x$x and $y$y.
Determine which of the following graphs contains the line of best fit.
A
B
C
DUse the line of best fit to estimate the value of $y$y when $x=4.5$x=4.5.
$4.5$4.5
A$5$5
B$5.5$5.5
C$6$6
DUse the line of best fit to estimate the value of $y$y when $x=9$x=9.
$6.5$6.5
A$7$7
B$8.4$8.4
C$9.5$9.5
D