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?

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

   Ren plotted ten classmates' heights against the minutes each took to finish a paper maze. Which answer names the association and gives a good reason?

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

   Ari tossed a play ball straight up, filmed it, and plotted its height every two tenths of a second. Which sentence describes the pattern of the dots?

   • A linear association: the dots tend to stay near one straight ruler line, with no bend.
   • 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.

   Bo counted the kids on the playground each hour after the park opened. It was the first warm day in weeks. Which sentence describes the pattern of the dots?

   • A nonlinear association: the dots tend to follow a curve, not one straight line.
   • No association: the dots tend to show no clear pattern.
   • A linear association: the dots tend to stay near one straight ruler line, going up steadily.
6. 6.

   Kira put a cup of juice in the freezer to make ice pops and checked its temperature every ten minutes. Which sentence describes the pattern of the dots?

   • A linear association: the dots tend to stay near one straight ruler line, going down steadily.
   • A nonlinear association: the dots tend to follow a curve, not one straight line.
   • No association: the dots tend to show no clear pattern.
7. 7.

   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)
8. 8.

   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
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 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.
   • 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.
10. 10.

    Two groups rolled toy cars down ramps. The first group's cars had wobbly wheels, and Plot B is Ren's group. Which answer is right, with a good reason?

    • 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.
    • Plot A shows the stronger association, because its first dot sits higher.
    • Plot B shows the stronger association, because its ruler line is steeper.