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

   Noah plotted the number of swimmers at the pool against the hour of the day. The calculator gives r = 0.01. Which statement is true?

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

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

   • There is a strong positive straight-line link.
   • 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.
7. 7.

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

   • The dots follow a clear curve; r near 0 only means no straight-line link.
   • There is a strong positive straight-line link.
   • The fit line is nearly flat, so the growth barely changes.
   • There is no relationship between the two at all.
8. 8.

   Tala plotted the outdoor temperature against the hour of a summer day. The calculator gives r = -0.01. Which statement is true?

   • The fit line is nearly flat, so the temperature barely changes.
   • The dots follow a clear curve; r near 0 only means no straight-line link.
   • There is a strong positive straight-line link.
   • There is no relationship between the two at all.
9. 9.

   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.
10. 10.

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

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