1. Grade Distribution 3rd 5th 8th A 7 4 3 B 6 5 C 2 1 D F 11 9 100+F 11 9
100+
No Shows
Range
43-99
37-99
52-99
Avg
75.9
69.5
72.4

3. Scatterplots
©2012

4. Definitions
A scatter plot is a graph with points plotted to show a possible relationship between two sets of data. A scatter plot is an effective way to some types of data.
A correlation describes a relationship between two data sets. A graph may show the correlation between data. The correlation can help you analyze trends and make predictions. There are three types of correlations between data.
Positive: Positive Slope
Negative: Negative Slope
No Correlation: No Slope

5. Positive Correlation;
Example 1
“The number of people in an audience and ticket sales.” Identify the correlation you would expect to see between the pair of data sets. Explain.
Positive Correlation;
As the number of people in the audience increases, ticket sales increase.

6. Negative Correlation;
Example 2
“A runner’s time and the distance to the finish line.” Identify the correlation you would expect to see between the pair of data sets. Explain.
Negative Correlation;
As a runner’s time increases, the distance to the finish line decreases.

7. Example 3
“The temperature in Houston and the number of cars sold in Boston.” Identify the correlation you would expect to see between the pair of data sets. Explain.
No Correlation;
The temperature in Houston has nothing to do with the number of cars sold in Boston.

8. Negative Correlation;
Your Turn
“The number of times you sharpen your pencil and the length of your pencil.” Identify the correlation you would expect to see between the pair of data sets. Explain.
Negative Correlation;
As the number of times you sharpen your pencil increases, the length of your pencil decreases.

9. Example 4
Which graph is the best scatter plot that best represents the relationship between the age of a car and the amount of money spent each year on repairs. Explain.
Graph A
Graph B
Graph C
Graph B

10. Your Turn
Which graph is the best scatter plot that best represents the number of minutes since a pie has been taken out of the oven and the temperature of the pie. Explain.
Graph A
Graph B
Graph C
Graph A

11. Trend Lines Create a Quadrant I graph
Label the axis and plot the points given
Draw a line:
Trend line is a graph where show the correlation between data sets more clearly. It can also be helpful when making predictions based on the data.

12. Example 5
The scatter plot shows a relationship between the total amount of money collected at the concession stand and the total number of tickets sold at a movie theater. Based on this relationship, predict how much money will be collected at the concession stand when 150 tickets have been sold.
Draw a trend line and use it to make a prediction.
Based on the data, $750 is a reasonable prediction of how much money will be collected when 150 tickets have been sold.

13. Example 6
A fundraiser is being held for school. Money is raised based on the number of Holiday wrapping paper is sold. For 25 rolls sold, the money raised is $190. For 55 rolls sold, $300 is sold. For 75 rolls sold, $510 is made. For 100 rolls sold, $710 is received. 140 rolls sold, $820 is made rolls sold for $1,000. Create a trend line and determine how much wrapping paper rolls need to be sold to raise $500.

14. Example 6
A fundraiser is being held for school. Money is raised based on the number of Holiday wrapping paper is sold. For 25 rolls sold, the money raised is $190. For 55 rolls sold, $300 is sold. For 75 rolls sold, $510 is made. For 100 rolls sold, $710 is received. 140 rolls sold, $820 is made rolls sold for $1,000. Create a trend line and determine how much wrapping paper rolls need to be sold to raise $500.
Based on the data, about 75 wrapping paper rolls is a reasonable prediction of how many rolls need to be sold to raise $500.

15. Your Turn
Neal kept track of the number of minutes it took for him to assemble sandwiches at his restaurant. Determine the correlation, trend line, and predict the time it will take for Neal to assemble 12 sandwiches.
Positive Correlation, about 10 minutes

16. 2.6: Scatter Plots and Best-Fit Lines
Steps of Curve Fitting
Identify and list all of the data points
In the graphs, enter the data using STAT L1 should be the independent variable and L2 should be the dependent variable
STAT  CALC  select LinReg (ax + b) to get the equation
11/14/2018
2.6: Scatter Plots and Best-Fit Lines

17. Example 7
The table shows the number of participants in U.S. Youth softball during the period of
Use the graphing calculator to find and graph the equation of the best-fitting line. (Round to the nearest thousandths)
What type of graph does this correlation represent? x
1997
1998
1999
2000
2001 y
1.44
1.4
1.411
1.37
1.355 x
1997
1998
1999
2000
2001 y
1.44
1.4
1.411
1.37
1.355

18. 2.6: Scatter Plots and Best-Fit Lines
Example 7
The table shows the number of participants in U.S. Youth softball during the period of
Use the graphing calculator to find and graph the equation of the best-fitting line. (Round to the nearest thousandths) x
1997
1998
1999
2000
2001 y
1.44
1.4
1.411
1.37
1.355
11/14/2018
2.6: Scatter Plots and Best-Fit Lines

19. Example 8
The table shows the median floor area of new single-family houses in the US during
Use the graphing calculator to find and graph the equation of the best-fitting line. (Round to the nearest tenths)
What type of graph does this correlation represent? x
1995
1996
1997
1998
1999 y
1920
1950
1975
2000
2028

20. Your Turn
The table shows the living space recommended for pigs of certain weights
Use the graphing calculator to find and graph the equation of the best-fitting line. (Round to the nearest tenths)
What type of graph does this correlation represent?
Weight 40 60 80
100
120
Area
2.5 3
3.5 4 5