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.

   Nearly all, 99.7%, of the eggs Tala weighs at a farm lie between 44 g and 80 g. The data are roughly normal. What is the standard deviation?

   6
4. 4.

   The middle 95% of the minutes Zee's classmates read each week lie between 140 and 180 minutes. The data are roughly normal. What is the standard deviation?

   10
5. 5.

   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
6. 6.

   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
7. 7.

   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
8. 8.

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

   • Class B: 16%, against 2.5%
   • Class A: 16%, against 2.5%
   • Class A: its taller curve holds more of the values
   • The same percent, because the means are equal
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
   • The same percent, because the means are equal
   • Group A: 99.7%, against 68%
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 A: 95%, against 68%
    • Team B: its wider curve covers more of the line
    • Team B: 95%, against 68%