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?

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

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

   • 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.
   • Strong and positive: as the wing width goes up, the flight distance tends to go up.
   • Strong and negative: as the wing width goes up, the flight distance tends to go down.
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?

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

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

   • 0.24
   • 0.97
   • 2
   • -0.97
5. 5.

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

   • -2
   • -0.24
   • -0.95
   • 0.95
6. 6.

   Ren plotted kite heights against wind speed. The calculator's line has slope 1.9. Which value is r for these dots?

   • -0.26
   • 1.9
   • 0.26
   • 0.93
7. 7.

   Tala plotted long-jump distances against minutes of warm-up. The calculator's line has slope 2. Which value is r for these dots?

   • 2
   • 0.93
   • -0.31
   • 0.31
8. 8.

   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?

   • Set A, because -0.97 is closer to -1 than 0.6 is to 1.
   • Set B, because 0.6 is greater than -0.97, so it is the stronger set.
   • Set B, because a positive r is stronger.
   • They are equally strong.
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 A, because 0.97 is closer to 1 than 0.58.
   • Set B, because its line is steeper, so the link is tighter.
   • They are equally strong.
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.