1. Algebra 1
Section 6.6

2. Possible Color Choices for this slide:

3. Scatterplots
Scatterplots are used to illustrate the relationship between two groups of data.
A trend line can often be drawn to show the relationship more clearly.

4. Scatterplots
The line of best fit, which can be found with graphing calculators or spreadsheets, is an exact equation of the trend line.

5. Example 1
Carefully estimate and draw a trend line that by visual inspection minimizes the distances to the data points.
Choose two points on the trend line.

6. Example 1
Find the equation of the line passing through those two points.
y = 0.3x – 651.3

7. Example 1

8. Example 1

9. Definitions
Interpolation is the process of making predictions within the range of the existing data points.
Extrapolation makes predictions outside this range.

10. Definitions
Interpolation tends to be more accurate than extrapolation.

11. Definitions
The linear correlation of the data describes how closely the data points are clustered along the trend line.

12. Definitions
There is a strong correlation when the majority of the points are close to the line.
Data with stronger correlations are more likely to produce accurate predictions.

13. Definitions
Data with a trend line from lower left to upper right has a positive correlation.
Data with a trend line from upper left to lower right has a negative correlation.

14. strong positive correlation weak positive correlation

15. strong negative correlation weak negative correlation

16. little or no correlation

17. Homework: pp