Line of Best Fit4.2 A

Goal

• Understand a scatter plot, and what makes a line a good fit to data.

Scatter plot

• Recall, data is often linear, but does not fall exactly on a line.

Line of Best Fit

• We draw a line to estimate the data called a “line of best fit”

Need 2 things!1. The slope of the line is

in the general direction of the points.

2. There are about half the points above the line, and half below the line.

Example

Example

Example

• Both are following the direction, and both have the same number of points above and below.

• How would your predictions differ if you use line t versus line s?

Remember when…

• We found equations from a table of data? Let’s do it again!

ExampleTime (hours)

Distance (miles)

2 150

5 400

Find the slope of this data, and include units in your answer.

Remember! Slope is rate of change.

or

83.3 mph

Homework

• Practice writing equations of lines, and drawing lines of best fit.