Sample means, margin of error and confidence intervals

Answer Key - Grade 11 Math Worksheet

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

1. 1.

   Bo's random sample of 80 students read a mean of 34 minutes a night. Using 2 standard deviations of the simulated dots as the margin, what is the upper end of the interval, in minutes?

   39
2. 2.

   Dot plot of 200 simulated sample results; the standard deviation of the dots is 0.15 hours. Esme's random sample of 60 students slept a mean of 7.2 hours. Using 2 standard deviations of the simulated dots as the margin, what is the lower end of the interval, in hours?

   6.9
3. 3.

   Jun's random sample of 150 students found 64% recycle at home. Using 2 standard deviations of the simulated dots as the margin, what is the lower end of the interval?

   56
4. 4.

   Dot plot of 200 simulated sample results; the standard deviation of the dots is 1.2 cm. Kira's random sample of 40 bean plants had a mean height of 22.5 cm. Using 2 standard deviations of the simulated dots as the margin, what is the upper end of the interval, in cm?

   24.9
5. 5.

   Luz plans a random sample of 400 students about reading time. Using 1/√n, what is the approximate margin of error, as a percent?

   5
6. 6.

   Milo plans a random sample of 625 students about recycling. Using 1/√n, what is the approximate margin of error, as a percent?

   4
7. 7.

   Pia reads that a district survey about bus rides will use a random sample of 1,600 students. Using 1/√n, what is the approximate margin of error, as a percent?

   2.5
8. 8.

   Ren reads that a state survey about sleep will use a random sample of 2,500 students. Using 1/√n, what is the approximate margin of error, as a percent?

   2
9. 9.

   In Zee's random sample of 200 bus riders, the mean bus ride was 18 minutes, with a margin of error of 2.5 minutes. Which statement is right?

   • Every bus rider at the school rides between 15.5 and 20.5 minutes, without exception.
   • The mean for all the school's bus riders is likely between 15.5 and 20.5 minutes.
   • The mean for all the school's bus riders is likely between 13 and 23 minutes.
   • The mean for all the school's bus riders is exactly 18 minutes.
10. 10.

    In Ari's random sample of 90 students, the mean sleep was 8.6 hours a night, with a margin of error of 0.3 hours. Which statement is right?

    • The mean for all the school's students is likely between 8.3 and 8.9 hours.
    • The mean for all the school's students is likely between 8 and 9.2 hours.
    • The mean for all the school's students is exactly 8.6 hours.
    • Every student at the school sleeps between 8.3 and 8.9 hours a night.