The correlation coefficient r, and correlation is not causation

Grade 9 Math Worksheet

Circle the best answer.

1. 1.

   Jun plotted mistakes in a song against daily practice time. The calculator gives r = -0.97. Which sentence describes the association?

   • Strong and positive: as the practice time goes up, the number of mistakes tends to go up a lot.
   • Weak and negative: the number of mistakes tends to go down a little, with lots of scatter.
   • Weak and positive: the number of mistakes tends to go up a little, with lots of scatter.
   • Strong and negative: as the practice time goes up, the number of mistakes tends to go down.
2. 2.

   Kira plotted kite heights against wind speed. The calculator gives r = 0.18. Which sentence describes the association?

   • Strong and positive: as the wind speed goes up, the kite height tends to go up.
   • Weak and positive: the kite height tends to go up a little, with lots of scatter.
   • Strong and negative: as the wind speed goes up, the kite height tends to go down.
   • Weak and negative: the kite height tends to go down a little, with lots of scatter.
3. 3.

   Luz plotted sprouted seeds against seeds planted. The calculator gives r = 0.97. Which sentence describes the association?

   • Weak and negative: the number that sprouted tends to go down a little, with lots of scatter.
   • Weak and positive: the number that sprouted tends to go up a little, with lots of scatter.
   • Strong and positive: as the number of seeds planted goes up, the number that sprouted tends to go up.
   • Strong and negative: as the number of seeds planted goes up, the number that sprouted tends to go down.
4. 4.

   Milo plotted hats in the lost and found against the temperature. The calculator gives r = -0.34. Which sentence describes the association?

   • Weak and positive: the number of hats tends to go up a little, with lots of scatter.
   • Strong and positive: as the temperature goes up, the number of hats tends to go up.
   • Weak and negative: the number of hats tends to go down a little, with lots of scatter.
   • Strong and negative: as the temperature goes up, the number of hats tends to go down a lot.
5. 5.

   Noah made two plots: Set A, song mistakes by practice time, has r = -0.89. Set B, paper airplane flights by wing width, has r = 0.61. Which set shows the stronger linear association?

   • Set B, because a positive r is stronger than a negative r.
   • They are equally strong.
   • Set A, because -0.89 is closer to -1 than 0.61 is to 1.
   • Set B, because 0.61 is greater than -0.89.
6. 6.

   Pia made two plots: Set A, cocoa sales by temperature, has r = -0.98. Set B, lemonade sales by temperature, has r = 0.54. Which set shows the stronger linear association?

   • Set A, because -0.98 is closer to -1 than 0.54 is to 1.
   • Set B, because 0.54 is greater than -0.98.
   • They are equally strong.
   • Set B, because a positive r is stronger than a negative one.
7. 7.

   Ren made two plots: Set A, lemonade sales by temperature, has r = 0.71. Set B, sprouts by seeds planted, has r = 0.98. Which set shows the stronger linear association?

   • Set A, because its line is steeper.
   • They are equally strong.
   • Set B, because 0.98 is closer to 1 than 0.71.
8. 8.

   Tala made two plots: Set A, paper airplane flights by wing width, has r = 0.97. Set B, kite heights by wind speed, has r = 0.69. Which set shows the stronger linear association?

   • Set B, because its line is steeper.
   • They are equally strong.
   • Set A, because 0.97 is closer to 1 than 0.69.
9. 9.

   Zee plotted beach-shop sunglasses sales against lemonade sales. The calculator gives r = 0.97. Which is the best explanation for the link?

   • r = 0.97 is so close to 1 that one must cause the other one.
   • Buying sunglasses makes people buy lemonade.
   • Drinking lemonade makes people buy sunglasses.
   • A third thing, hot, sunny weather, tends to push both up.
10. 10.

    Ari plotted mittens in the lost and found against soup sold. The calculator gives r = 0.97. Which is the best explanation for the link?

    • Losing mittens makes students buy soup.
    • A third thing, cold weather, tends to push both up.
    • r = 0.97 is so close to 1 that one must cause the other.
    • Buying soup makes students lose mittens.