Transcript Unit 6 Scatter Plots A scatter plot is a graph with points plotted to show a relationship between two sets of data. Correlation describes.

Unit 6
Scatter Plots
A scatter plot is a graph with points plotted to
show a relationship between two sets of data.
Correlation describes the type of relationship
between two data sets.
The line of best fit is the line that comes
closest to all the points on a scatter plot. One
way to estimate the line of best fit is to lay a
ruler’s edge over the graph and adjust it until it
looks closest to all the points.
Unit 6
Scatter Plots
Positive
correlation:
both data
sets increase
together.
Negative
correlation:
as one data
set increases,
the other
decreases.
No
correlation:
changes in
one data set
do not affect
the other
data set.
Non-Linear:
No straight
line of best fit
can be
formed
through the
points.
Unit 6
Scatter Plots
Do the data sets have a positive, a negative,
or no correlation?
The size of a jar of baby food and the number
of jars of baby food a baby will eat.
Negative correlation: The more food in each
jar, the fewer number of jars of baby food a baby
will eat.
Unit 6
Scatter Plots
Do the data sets have a positive, a negative,
or no correlation?
The speed of a runner and the number of
races she wins.
Positive correlation: The faster the runner, the
more races she will win.
Unit 6
Scatter Plots
Do the data sets have a positive, a negative,
or no correlation?
The size of a person and the number of
fingers he has.
No correlation: The size of a person will not
affect the number of fingers a person has.
Unit 6
Scatter Plots
Example 1: Making a Scatter Plot of a Data Set
Use the given data to make a scatter plot of
the weight (y) and height (x)of each member
of a basketball team, and describe the
correlation.
The points on the scatter plot are
(71, 170), (68, 160), (70, 175),
(73, 180), and (74, 190).
There is a positive correlation between the two data
sets.
Unit 6
Scatter Plots
Example 2:
Use the given data to make a scatter plot of
the weight and height of each member of a
soccer team, and describe the correlation.
Weight (lbs)
63
125
67
156
69
175
68
135
62
120
200
190
180
Weight
Height (in)
170
160
150
140
The points on the scatter 130
plot are (63, 125), (67,
120
156), (69, 175), (68, 135),
and (62, 120).
60 61 62 63 64 65 66 67 68 69
Height
There is a positive correlation between the two data sets.
Scatter Plots
Line of Best Fit…
A line that comes close to all
the points on a scatter plot.
Hint: Try to draw the line so
that about the same number
of points are above the line
as below the line.
Unit 6
Scatter Plots
Example 3: Using a Scatter plot to Make Predictions
Make a scatter plot of the data, and draw a line
of best fit. Then use the data to predict how
much a worker will earn in tips in 10 hours.
Step 1: Make a scatter plot.
Let hours worked represent
the independent variable x
and tips earned represent the
dependent variable y.
Tips earned may be
dependent on the
number of hours
worked.
Unit 6
Scatter Plots
Additional Example 2 Continued
Step 2: Draw a line of best fit.
Draw a line that has about the same number of
points above and below it.
Unit 6
Scatter Plots
Additional Example 2 Continued
Step 3: Make a prediction.
According to the graph, working 10 hours will earn
about $24 in tips.
Find the point on the
line whose x-value is
10. The corresponding
y-value is about 24.
Unit 6
Scatter Plots
Formative Assessment:
Are you really getting scatter plots and lines of best fit??
Unit 6
Scatter Plots
1. Use the given information to make a scatter
plot, and describe the correlation.
Grading Period 1
2 3
Number of A’s
6 8 10
5
positive correlation
4
Unit 6
Scatter Plots
2. Draw a line of best fit for the scatter plot you
drew in Problem 1. Then use the data to predict
the number of A’s in grading period 6.
approximately 13 A’s
Unit 6
Scatter Plots
1. Identify a scatter plot for the given data.
A.
B.
Unit 6
Scatter Plots
2. Do the data sets have a positive, a negative, or
no correlation?
distance covered and time taken at constant speed
A. positive
B. negative
C. none
Unit 6
Scatter Plots
3. Do the data sets have a positive, a negative, or
no correlation?
value of a used car and the total distance traveled
A. positive
B. negative
C. none