The correlation coefficient r, and correlation is not causation

Grade 9 Math Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Jun plotted hot cocoa sales against the temperature. The calculator gives r = -0.96. Which sentence describes the association?

   • Weak and negative: the number of mugs sold tends to go down a little, with lots of scatter.
   • Weak and positive: the number of mugs sold tends to go up a little, with lots of scatter.
   • Strong and positive: as the temperature goes up, the number of mugs sold tends to go up.
   • Strong and negative: as the temperature goes up, the number of mugs sold tends to go down.
2. 2.

   Kira plotted paper airplane flights against wing width. The calculator gives r = 0.22. Which sentence describes the association?

   • Strong and negative: as the wing width goes up, the flight distance tends to go down.
   • Strong and positive: as the wing width goes up, the flight distance tends to go up.
   • Weak and positive: the flight distance tends to go up a little, with lots of scatter.
   • Weak and negative: the flight distance tends to go down a little, with lots of scatter.
3. 3.

   Luz plotted how far a toy car rolls against the ramp height. The calculator gives r = 0.96. Which sentence describes the association?

   • Strong and positive: as the ramp height goes up, the distance rolled tends to go up.
   • Weak and positive: the distance rolled tends to go up a little, with lots of scatter.
   • Strong and negative: as the ramp height goes up, the distance rolled tends to go down.
   • Weak and negative: the distance rolled tends to go down a little, with lots of scatter.
4. 4.

   Milo plotted books read this year against birthday date. The calculator gives r = -0.38. Which sentence describes the association?

   • Weak and negative: the number of books read tends to go down a little, with lots of scatter.
   • Strong and positive: as the birthday date goes up, the number of books read tends to go up.
   • Weak and positive: the number of books read tends to go up a little, with lots of scatter.
   • Strong and negative: as the birthday date goes up, the number of books read tends to go down.
5. 5.

   Noah plotted lemonade sales against the temperature. The calculator's line has slope 2. Which value is r for these dots?

   • -0.97
   • 0.97
   • 2
   • 0.24
6. 6.

   Pia plotted kids on the playground against snow depth. The calculator's line has slope -2. Which value is r for these dots?

   • -0.24
   • -0.95
   • 0.95
   • -2
7. 7.

   Zee made two plots: Set A, kids outside by snow depth, has r = -0.97. Set B, paper airplane flights by wing width, has r = 0.6. Which set shows the stronger linear association?

   • They are equally strong.
   • Set B, because a positive r is stronger.
   • Set B, because 0.6 is greater than -0.97, so it is the stronger set.
   • Set A, because -0.97 is closer to -1 than 0.6 is to 1.
8. 8.

   Ari made two plots: Set A, kite heights by wind speed, has r = 0.58. Set B, cocoa sales by temperature, has r = -0.97. Which set shows the stronger linear association?

   • Set A, because 0.58 is greater than -0.97.
   • They are equally strong.
   • Set A, because a positive r is stronger.
   • Set B, because -0.97 is closer to -1 than 0.58 is to 1.
9. 9.

   Bo made two plots: Set A, sprouts by seeds planted, has r = 0.97. Set B, kite heights by wind speed, has r = 0.58. Which set shows the stronger linear association?

   • Set B, because its line is steeper, so the link is tighter.
   • They are equally strong.
   • Set A, because 0.97 is closer to 1 than 0.58.
10. 10.

    Esme made two plots: Set A, paper airplane flights by wing width, has r = 0.97. Set B, kite heights by wind speed, has r = 0.53. Which set shows the stronger linear association?

    • Set A, because 0.97 is closer to 1 than 0.53.
    • They are equally strong.
    • Set B, because its line is steeper.