Scatter Plots and Trend Lines

Name______Date______Class______

Problem Solving

Scatter Plots and Trend Lines

Fawn is trying to improve her reading skills by taking a speed-
reading class. She is measuring how many words per minute (wpm) she can read after each week of the class.

Holt McDougal Coordinate Algebra

Name______Date______Class______

1.Graph a scatter plot using the given
data.

Weeks / 1 / 2 / 3 / 4 / 5
wpm / 220 / 230 / 260 / 260 / 280

2.Describe the correlation illustrated by the scatter plot.

______

3.Draw a trend line and use it to predict the number of words per minute that Fawn will read after 8 weeks of this class.

______

4.Fawn is paying for this class each week out of her savings account. Identify the correlation between the number of classes and Fawn’s account balance.

______

Holt McDougal Coordinate Algebra

Name______Date______Class______

Choose the scatter plot that best represents the described relationship.

5.the distance a person runs and how
physically tired that person is

AGraph 1CGraph 3

BGraph 2DGraph 4

6.the price of a new car and the number of
hours in a day

FGraph 1HGraph 3

GGraph 2JGraph 4

7.a person’s age and the amount of
broccoli the person eats

AGraph 1CGraph 3

BGraph 2DGraph 4

8.the number of cats in a barn and the
number of mice in that barn

FGraph 1HGraph 3

GGraph 2JGraph 4

Holt McDougal Coordinate Algebra

Name______Date______Class______

4-5.

6.Possible answer: slight negative correlation or no correlation

7.about 23.8 gallons per person

8.Possible answer: not very confident; the data fluctuates a lot from year to year.

Review for Mastery

1.Negative correlation; each knot decreases the length of the rope

2.No correlation; there is no relationship between height and algebra skill

3.negative correlation

4.positive correlation

6.Possible answer: 8 mi/gal

Possible answer: 20 mi/gal

Possible answer: 4.5 L

Possible answer: 1.4 L

Challenge

1.Yes, all the data points are either on the lines or between them.

2.3 units; 2 units

4.The closer together the parallel bounding lines are, the more tightly the data cluster around a line. The farther apart the parallel bounding lines are, the more loosely the data points cluster around a line.

Problem Solving

2.positive correlation

3.about 320 wpm

4. negative correlation

5.C6.J

7.B8.F

Reading Strategies

1.number of children in a family; monthly cost of food; increases; positive

2.population of cities in the U.S.; average February temperature; shows no pattern; none

3.number of practice runs; finish time; decreases; negative

Line of Best Fit

Practice A

1a.6

b.6

c.neither

2a.

b.≈ 0.997

c.very well

d.strong pos. correlation

3a.

b.≈ –0.997

c.very well

d.strong neg. correlation

4.strong pos. correlation; likely
cause-and-effect relationship

Practice B

1a.134

b.10

2a.

b.0.46

c.moderately well

d.weak pos. correlation

3a.

b.0.99

c.very well

d.strong neg. correlation

4.strong pos. correlation; unlikely
cause-and-effect relationship

Practice C

1a.26

2a.

b.0.53

c.not well

d.weak pos. correlation

3a.

b.0.99

c.very well

d.strong pos. correlation

4.strong neg. correlation; likely
cause-and-effect relationship

Review for Mastery

1a.8, 7, 6, 5

b. 8, 0; 7, –2; 6, –1; 5, –3

c. 0, –2, –1, –3; 0, 4, 1, 9; 14

3.1.51; 12.90

1.51; 12.90

0.93; strong neg.

Challenge

2.6x – 64.0.98

5.x2 + 17.1

8.Possible answer: r 0.98 for y 6x 6, which means there is a strong positive correlation and that the linear equation is a very good model of the data; however, r 1 for yx2 1, which means the

Holt McDougal Coordinate Algebra