1. 1.5 Scatter Plots & Line of Best Fit

2. Scatter Plots A scatter plot is a graph that shows the relationship between two sets of data. In a scatter plot, two sets of data are graphed as ordered pairs on a coordinate system.

3. Making a Scatter Plot The table shows the average SAT math scores from 1990–2000. Make a scatter plot of the data. Each combination of (Year, Score) makes an ordered pair that can be graphed on the coordinate plane.

4. Making a Scatter Plot STEP 1: Label your axes. The independent variable goes on the x-axis and the dependent variable goes on the y-axis.

5. Making a Scatter Plot STEP 2: Determine a scale. This does not have to be the same on each axis, but the interval has to stay the same between each line. Use a break when you want to "skip" values at the beginning of the axis.

6. Making a Scatter Plot STEP 3: Plot the data as ordered pairs. DO NOT CONNECT THE POINTS!

7. Interpreting Scatter Plots You can use scatter plots to determine if there is a relationship, or correlation, between two sets of data. Three types of correlations are... Positive, Negative or No Correlation.

8. Interpreting Scatter Plots

9. Would a scatter plot of the following data show a positive, negative, or no correlation? 1. car age vs. car value As the age of a car increases, the value of the car decreases. So, a scatter plot of the data would show a negative relationship.

10. Interpreting Scatter Plots Would a scatter plot of the following data show a positive, negative, or no correlation? 2. birth month vs. birth weight A person’s birth weight is not affected by their birth month. Therefore, a scatter plot of the data would show no relationship.

11. Best-Fit Lines When real-life data are collected, the points graphed usually do not form a straight line, but may approximate a linear relationship. A best-fit line can be used to show such a relationship. A best-fit line is a line that is very close to most of the data points.

12. Line of Best Fit The table shows the number of years people in the United States are expected to live, according to the year they were born. Draw a scatter plot for this data. Year of Birth 192 0 19301940195019601970198019902000 Life Expec tancy 546063687071747576

13. Draw a line that passes through as many points as possible. This line does not need to pass through the origin. Try to have an equal number of points above and below the line.

14. 1.5 Practice Problems Pg. 35 #1 (Tape the provided graph in your notebook), 3-11, 16