Scatter plots: patterns of association

Answer Key - Grade 8 Math Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Noah's music club plotted minutes of guitar practice a day against chord changes made in one minute. Which answer names the association and gives a good reason?

   • No association, because the dots do not all lie exactly on one line.
   • A negative association, because a ruler line through the middle of the dots rises from left to right.
   • No association, because 10 dots are too few to show a pattern.
   • A positive association, because a ruler line through the middle of the dots rises from left to right.
2. 2.

   Pia's running club timed one lap each week of training and plotted the results. The club's cheer got louder every week. Which answer names the association and gives a good reason?

   • A positive association, because a ruler line through the middle of the dots falls from left to right.
   • A negative association, because a ruler line through the middle of the dots falls from left to right.
   • No association, because 10 dots are too few to show a pattern.
   • No association, because the dots do not all lie exactly on one line.
3. 3.

   Esme plotted the temperature at kickoff against the goals Esme's team scored in ten soccer games. Which answer names the association and gives a good reason?

   • No association, because the left half and the right half of the dots spread over about the same y-values.
   • A negative association, because the right-most dot sits lower than the left-most dot.
   • A positive association, because a ruler line through the middle of the dots rises from left to right.
4. 4.

   Luz rolled a toy car down a ramp set at different heights and measured how far it rolled. Which sentence describes the pattern of the dots?

   • A linear association: the dots tend to stay near one straight ruler line.
   • No association: the dots tend to show no clear pattern.
   • A nonlinear association: the dots tend to follow a curve, not one straight line.
5. 5.

   Kira measured a tomato plant every week for twelve weeks. One week, the ruler slipped. Which point is the outlier, written as (x, y)?

   (6, 30)
6. 6.

   Tala timed twelve bike rides of different lengths. On one ride, a strong wind pushed from behind the whole way. Which point is the outlier, written as (x, y)?

   (30, 50)
7. 7.

   At the harbor, Zee measured sailboat lengths and mast heights. One dot is an outlier. How many boats are in the cluster of bigger boats?

   6
8. 8.

   In the park, Luz measured trunk widths and tree heights. One dot is an outlier. How many trees are in the cluster of thinner trees?

   6
9. 9.

   Two classes grew bean plants and plotted days against height. Plot A is Ari's class. Which answer is right, with a good reason?

   • Plot B shows the stronger association, because its dots reach higher on the grid.
   • The two plots show the same strength, because each plot has 8 dots.
   • Plot A shows the stronger association, because its dots stay closer to its ruler line.
   • Plot B shows the stronger association, because its ruler line is steeper.
10. 10.

    Milo flew big kites (Plot A) and small kites (Plot B) and plotted wind speed against kite height. Which answer is right, with a good reason?

    • Plot A shows the stronger association, because its dots reach higher on the grid.
    • Plot A shows the stronger association, because its ruler line is steeper and climbs higher.
    • The two plots show the same strength, because each plot has 8 dots.
    • Plot B shows the stronger association, because its dots stay closer to its ruler line.