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1.5 Scatter Plots and Lines of Best FitEssential Questions: How can I use ascatter plot to draw informal inferenceabout the correlation between twovariables? How do I determine an equationfor the line of best fit using a graphingcalculator?
In many realworld problems, youwill find data that relate twovariables such as time anddistance or age and height. Youcan view the relationship betweentwo variables with a scatter plot.
A scatter plot is the graph of the ordered pairs that describe
a relationship betweentwo sets of data.
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Correlation
Positive correlation Negative correlation
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No correlation
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Let's collectsome data.
Name Age (in years)
Height(in inches)
Wingspan(in inches)
# of Letters in Last Name
Celina
Ally
Jajaun
Luke
Quad'gee
Sarah
Dede
Jordan
Taylor
Chanel
Lauren
Myeisha
Michael Ma.
Mike Mo.
Caitlyn
Nicolette
DeVante
Celia
Aaron
Jackie
Haimbach
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Line of Best Fit
A scatter plot can help you see patterns in data involving two variables. A line of best fit is a linear model that fits that data.
Part 1: Input the data from the table into your calculator:1) Stat2) Edit3) Input ages into L1, height into L2, wingspan into L3, and number of letters in last name in L4
Part 2: Make it so that you will be able to see the points on a graph:
1) 2nd2) Y =3) Go into the first stat plot4) Turn the stat plot on5) Make sure that L1 is used for x and L2 is used for y
Line of Best Fit continued
Part 3: View the graph:1) Window2) Find the minimum and maximum values for x from the table. Set appropriate values for the xmin, xmax, and xscl.3) Find the minimum and maximum values for y from the table,
and set appropriate values for the ymin, ymax, and yscl.4) Graph
Part 4: Write the line of best fit:1) Stat2) Calc3) 4: LinReg (ax + b) L2, L34) EnterThis gives you the equation for the line of best fit.