Name _______________________________________ Date __________________ Class __________________
Data, Prediction, and Linear Functions
SECTION A Family Letter: Data and Prediction
Dear Family,
Students will be learning about scatter plots. A scatter plot is
a graph with points plotted to show a relationship between two
sets of data. By studying the grouping of the points, you can
tell whether or not the two sets of data are related. This is
called a correlation.
If both sets of data increase or decrease together, they have
a positive correlation. If one set increases as the other set
decreases, they have a negative correlation. A correlation is
said to be strong or weak depending on how closely the data
sets follow the positive or negative pattern. Sometimes one
data set has no apparent effect on the other set. These data
sets have no correlation.
Make a scatter plot and describe the correlation.
There is a strong positive correlation between study time and
test scores. The more time spent studying, the higher the test
score.
Sincerely,
Ms. Galanis
Holt McDougal Mathematics
Name _______________________________________ Date __________________ Class __________________
Data, Prediction, and Linear Functions
SECTION A Family Letter: Data and Prediction continued
Students will also learn about lines of best fit. When you draw
a line on a scatter plot so that it comes closest to most of the
points on the scatter plot, you have found a line of best fit.
On the graph shown below, the points are the scatter plot and
the line is a linear best fit model. This line is used to make
predictions about the relationship of the data. The predictions
are usually made about points that might be part of the scatter
plot if the x- and y- scales were extended.
With any line of best fit, some points lie above the line, some
lie below the line and some line on line. The more points that
lie on the line, the more closely the line of best fit models the
data of the scatter plot.
Holt McDougal Mathematics
Name _______________________________________ Date __________________ Class __________________
Data, Prediction, and Linear Functions
SECTION A At-Home Practice: Data and Prediction
1. A group of students had babysitting jobs over the weekend. Use
the given data to make a scatter plot.
Name
Total Hours
Worked
Amount
Earned
Sheri
5
$22.50
Jordan
8
$36.00
Lydia
11
$49.50
Alexis
6
$27.00
2. Use the data from the scatter plot to predict the number of hours
Sam would have to work to make $30.
________________________________________________________________________________________
Do the sets of data have a positive, negative, or no correlation?
3. The weight of a baby and the month
that it is born.
4. The amount of free time you have and
the number of sports that you play.
________________________________________
_______________________________________
Use the scatter plot to answer questions 5-8.
A car manufacturer tracks the value of a certain model of car over
time as shown in the scatter plot below.
25000
y
22500
20000
Car Value
17500
15000
12500
10000
7500
5000
2500
1
2
3
4
5
6
7
8
9
x
Age (years)
5. Does the pattern of association
between car value and age appear to
be linear or non-linear?
6. Identify any outliers.
7. Is the correlation positive or
negative?
8. Predict the sales price when the age
is 10 years old.
Answers: 1. Points should be plotted at: (5, 22.50), (8, 36), (11, 49.50) and (6, 27): x-axis is hours worked, y-axis is
amount earned 2. about 7 hours 3. no correlation 4. negative correlation 5. non-linear 6. (5, 10,000) 7. negative
8. about $2,500
Holt McDougal Mathematics
Name _______________________________________ Date __________________ Class __________________
Data, Prediction, and Linear Functions
Family Fun: Graphing for Greatness
Unscramble the words below. Then look through the chapter to find
examples of each. Try to find at least two examples and write the
page numbers on which they appear.
1. T A C P O T S R L E T
___________________________________________________
Examples on pages
________________________________________________________
2. F E I I S E N F B T O L T
________________________________________________
Examples on pages
________________________________________________________
3. T S E R L C N U G I
_____________________________________________________
Examples on pages
________________________________________________________
4. R P S O E C O R T L V I E I A N O I T
____________________________________
Examples on pages
________________________________________________________
5. W T A T W Y O L E B A
_________________________________________________
Examples on pages
________________________________________________________
6. R R N E I T C O O L A A T N G V E I
_____________________________________
Examples on pages
________________________________________________________
Answers: 1. Scatterplot; 2. Line of best fit; 3. Clustering; 4. Positive correlation; 5. Two-way table; 6. Negative
correlation
Holt McDougal Mathematics