The correlation coefficient r, and correlation is not causation

Grade 9 Math Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Jun plotted lemonade sales against the temperature; r = 0.67. One day the stand ran out of cups early. If the dot (83, 18) is removed, what happens to r?

   • r moves closer to 0, because there are fewer dots.
   • r moves closer to 1, because the other dots hug a line.
   • r stays about the same, because one dot is too few to matter.
   • r becomes negative.
2. 2.

   Kira plotted bus ride times against miles from school; r = 0.75. One day the bus took a long detour. If the dot (5, 58) is removed, what happens to r?

   • r moves closer to 0, because there are fewer dots.
   • r moves closer to 1, because the other dots hug a line.
   • r becomes negative.
   • r stays about the same, because one dot is too few to matter.
3. 3.

   Luz plotted sprouted seeds against seeds planted; r = 0.97. One big tray held 60 seeds. If the dot (60, 49) is removed, what happens to r?

   • r moves closer to 0, because the other dots are scattered.
   • r moves closer to 1, because removing a far dot always helps.
   • r becomes exactly 1.
   • r stays about the same, because one dot is too few to matter.
4. 4.

   Milo plotted kite heights against wind speed; r = 0.9. One flight was on a very windy day. If the dot (24, 102) is removed, what happens to r?

   • r stays about the same, because one dot is too few to matter.
   • r moves closer to 1, because removing a far dot always helps.
   • r moves closer to 0, because the other dots are scattered.
   • r becomes exactly 1.
5. 5.

   Pia plotted coats worn to class against the month. The calculator gives r = 0.04. Which statement is true?

   • The dots follow a clear curve; r near 0 only means no straight-line link.
   • The fit line is nearly flat, so the number of coats barely changes.
   • There is no relationship between the two at all.
   • There is a strong positive straight-line link.
6. 6.

   Ren plotted how much a bean plant grew against the water it got. The calculator gives r = 0.05. Which statement is true?

   • The fit line is nearly flat, so the growth barely changes.
   • There is a strong positive straight-line link.
   • The dots follow a clear curve; r near 0 only means no straight-line link.
   • There is no relationship between the two at all.
7. 7.

   Zee plotted hot cocoa sales against the temperature, and the calculator gives r = -0.97. Which claim do the data support?

   • Each extra degree lowers the number of mugs sold by 0.97.
   • r = -0.97 is so close to -1 that it proves the temperature causes the change.
   • As the temperature goes up, the number of mugs sold tends to go up.
   • The link is strong and negative, but r alone cannot prove a cause.
8. 8.

   Ari plotted mistakes in a song against daily practice time, and the calculator gives r = -0.97. Which claim do the data support?

   • The link is strong and negative, but r alone cannot prove a cause.
   • As the practice time goes up, the number of mistakes tends to go up.
   • r = -0.97 is so close to -1 that it proves the practice time causes the change.
   • Each extra minute lowers the number of mistakes by 0.97.
9. 9.

   Bo plotted how far a toy car rolls against the ramp height, and the calculator gives r = 0.97. Which claim do the data support?

   • As the ramp height goes up, the distance rolled tends to go down.
   • Each extra centimeter raises the distance rolled by 0.97.
   • r = 0.97 is so close to 1 that it proves the ramp height causes the change.
   • The link is strong and positive, but r alone cannot prove a cause.
10. 10.

    Esme plotted bus ride times against miles from school, and the calculator gives r = 0.97. Which claim do the data support?

    • The link is strong and positive, but r alone cannot prove a cause.
    • Each extra mile raises the bus time by 0.97.
    • r = 0.97 is so close to 1 that it proves the distance from school causes the change.
    • As the distance from school goes up, the bus time tends to go down.