Intro to Scatterplots and Trend Lines

◼If there is a cluster or trend (positive or

negative) we can use the line of best fit,
or trend line,to make predictions.

MAKE PREDICTIONS

POSITIVE

NEGATIVE

NO

CORRELATION

◼Use a straight-edge to draw the line of best fit, or trend line.

◼Try to get approximately the same number of points above the
line of best fit as below the line.

How to Draw the Line of Best Fit:

◼ Since there is a positive correlation with the data, predict what a

student who earned a 75% on their history test earned on their
math test.

◼ What can I draw that will help me make that prediction?

HISTORY VS. MATH

◼ Is there a relationship with this data?
◼ What kind of relationship is it?
◼ If I have a goldfish population of 15, how many star fish will there

be?

◼ What can I draw to help me make that prediction?

GOLDFISH & STAR FISH

Multiple Choice

What is the age of a tree that is 34 feet tall?

• 7 years

• 10.5 years

• 13 years

• 25 years

Multiple Choice

How long will Melissa wait if there are 6 people in front of her?

• 14 minutes

• 12 minutes

• 8.5 minutes

• 3 minutes

◼ Draw a line of best fit.
◼ If I have a goldfish population of 15, how many star fish will there

be?

◼ There would be about 26 star fish.

GOLDFISH & STAR FISH

Multiple Choice

What would be the weight of a person who is 72 inches tall?

• About 180 lbs

• About 163 lbs

• About 153 lbs

• About 145 lbs

Multiple Choice

How many seconds for the elevator to reach the 50th floor?

• 24

• 21

• 28

• 19

Multiple Choice

How long does a person with 3 cavities brush their teeth?

• 1.75 minutes

• 4 minutes

• 1 minute

• 0.5 minutes

Multiple Choice

How many potatoes are in a 15 pound bag?

• 8

• 15

• 45

• 50

◼ Scatter Plots show Linear Associations when the points cluster

along a straight line.

PATTERNS IN SCATTER PLOTS

Linear Association

Linear Association

◼ Scatter Plots show Non-Linear Associations when the points do

not cluster along a straight line

PATTERNS IN SCATTER PLOTS

Non- Linear
Association

Non- Linear
Association

◼ Scatter Plots show a positive trend if y tends to

increase as x increases or if y tends to decrease as the x
decreases.

◼ Scatter Plots show a negative trend if one value tends

to increase and the other tends to decrease.

◼ A scatter plot shows no trend (correlation) if there is no

obvious pattern.

PATTERNS IN SCATTER PLOTS

POSITIVE

NEGATIVE

NO

CORRELATION

Multiple Choice

The police department tracked the number of ticket writers and number of tickets issued for the past 8 weeks.  The scatter plot shows the results.  Which statement is true?

• More ticket writers results in fewer tickets issued.

• There were 50 tickets issued every week.

• When there are 10 ticket writers, there will be 800 tickets issued.

• More ticket writers results in more tickets issued.

Multiple Choice

The following scatter plot shows the weights and lengths of some dinosaurs.  Which statement accurately describes the information?

• The information shows a positive correlation.  The weight of a dinosaur tends to increase according to its length.

• The information shows a negative correlation.  the weight of a dinosaur tends to decrease according to its length.

• The information shows no correlation.  The weight and length vary according to the type of dinosaur.

• The information shows no correlation.  The relationship between the weight and length of a dinosaur is uncertain.

Multiple Choice

The scatter plot shows the number of absences in a week for classes of different sizes.  Trevor concluded that there is a positive correlation.  Which statement best describes why Trevor's conclusion was incorrect.

• The largest class does not have the most absences.

• The smallest class does not have the least number of absences.

• The data show no relationship between class size and number of absences.

• The data show a negative relationship between class size and number of absences.

Multiple Choice

This scatter plot shows the average traffic volume and average vehicle speed on a certain freeway for 50 days in 1999.  Which statement best describes this relationship.

• As traffic volume increases, vehicle speed increases.

• As traffic volume increases, vehicle speed decreases.

• As traffic volume increases, vehicle speed increases at first, then decreases.

• As traffic volume increases, vehicle speed decreases at first, then increases.

Multiple Choice

Which graph shows the line of best fit?

• Graph A

• Graph B

• Graph C

• Graph D

Multiple Choice

Which scatter plot show a positive relationship?

• Graph A

• Graph B

• Graph C

• Graph D

Multiple Choice

What type of association does this scatter plot show?

• positive linear association

• negative linear association

• no association

• nonlinear association

Multiple Choice

What type of association does this scatter plot represent?

• positive linear association

• negative association

• no association

• nonlinear association

Multiple Choice

The daily attendance at a bowling alley was recorded for 15 days. The scatterplot shows the number of lanes rented each day and the number of people who bowled that day. Which statement is best supported by the scatterplot?

• There is a non-linear assocation between the number of lanes rented and the number of people who bowl.

• There is a negative linear association between the number of lanes rented and the number of people who bowl.

• There is no apparent association between the number of lanes rented and the number of people who bowl.

• There is a positive linear association between the number of lanes rented and the number of people who bowl.

Multiple Choice

What is the first step when calculating the Mean Absolute Deviation?

• Find the distance each value is from the mean

• Find the mean of the distances

• Find the mean of the data

Multiple Choice

What is the second step when calculating the Mean Absolute Deviation?

• Find the distance each value is from the mean

• Find the mean of the distances

• Find the mean of the data

Multiple Choice

What is the third step when calculating the Mean Absolute Deviation?

• Find the distance each value is from the mean

• Find the mean of the distances

• Find the mean of the data

Multiple Choice

Find the Mean Absolute Deviation:  10, 9, 3, 8, 10.  The Mean is 8.

• 3

• 5

• 1

• 2

Multiple Choice

Find the Mean Absolute Deviation:  5, 11, 2, 7, 16.  The Mean is 8.2 

• 3.2

• 2.8

• 1.2

• 4.2

Multiple Choice

Determine the mean absolute deviation of the data. 9, 7, 11, 10, and 8

• 9

• 6

• 1.2

• 5