The normal curve and the empirical rule

Answer Key - Grade 11 Math Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   The middle 95% of the plant heights in Pia's class lie between 38 cm and 62 cm. The data are roughly normal. What is the standard deviation?

   6
2. 2.

   The middle 68% of the times for Ren's class to tie a knot lie between 61 and 69 seconds. The data are roughly normal. What is the standard deviation?

   4
3. 3.

   Scores in Ari's class quiz game are roughly normal, with mean 60 and SD 8. Only 2.5% of scores are above which score?

   76
4. 4.

   Normal curve with its mean 120 marked and one SD, 6, drawn as an arrow from the mean. The heights of the sunflowers at Bo's school are roughly normal, with mean 120 cm and SD 6 cm. About 16% of heights are below which height?

   114
5. 5.

   The times for one relay leg in Esme's class are roughly normal, with mean 30 seconds and SD 4 seconds. About 84% of times are below which time?

   34
6. 6.

   The hours the flashlights in Jun's class run are roughly normal, with mean 9 and SD 0.5. Only 0.15% of run times are above which time?

   10.5
7. 7.

   Kira compares two classes' run times; both are normal with mean 60 s. Which class has the larger percent of times above 70 s?

   • The same percent, because the means are equal
   • Class B: 16%, against 2.5%
   • Class A: its taller curve holds more of the values
   • Class A: 16%, against 2.5%
8. 8.

   Luz compares two machines filling juice bottles; both fills are normal with mean 500 mL. Which machine fills the larger percent of bottles below 496 mL?

   • Machine A: 16%, against 2.5%
   • Machine B: 16%, against 2.5%
   • The same percent, because the means are equal
   • Machine A: its taller curve holds more of the values
9. 9.

   Milo compares two groups' plant heights; both are normal with mean 50 cm. Which group has the larger percent between 44 and 56 cm?

   • Group B: 99.7%, against 68%
   • Group B: its wider curve covers more of the line
   • Group A: 99.7%, against 68%
   • The same percent, because the means are equal
10. 10.

    Noah compares two teams' jump heights; both are normal with mean 100 cm. Which team has the larger percent between 90 and 110 cm?

    • The same percent, because the means are equal
    • Team B: its wider curve covers more of the line
    • Team B: 95%, against 68%
    • Team A: 95%, against 68%