Sample means, margin of error and confidence intervals

Answer Key - Grade 11 Math Worksheet - Building Confidence

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

1. 1.

   Ari drew 20 random samples of 25 students and plotted each sample's mean reading time as one dot. What is the mean of the 20 dots, in minutes?

   32.6
2. 2.

   Esme drew 20 random samples of 30 students and plotted each sample's mean hours of sleep as one dot. What is the mean of the 20 dots, in hours?

   8.15
3. 3.

   Jun drew 20 random samples of 12 bean plants and plotted each sample's mean height as one dot. What is the mean of the 20 dots, in cm?

   16.1
4. 4.

   Dot plot of 100 sample percents; the middle 95 dots run from 52% to 68%. Kira simulated 100 random samples of 100 students; each dot is one sample's percent who walk to school. What is the margin of error, in percentage points?

   8
5. 5.

   Luz simulated 100 random samples of 50 students; each dot is one sample's mean hours of sleep. What is the margin of error, in hours?

   0.4
6. 6.

   Milo simulated 200 random samples of 30 students; each dot is one sample's mean reading time. What is the margin of error, in minutes?

   6
7. 7.

   Pia simulated 100 random samples of 15 sunflowers; each dot is one sample's mean height. What is the margin of error, in cm?

   1.5
8. 8.

   Tala simulated percents who bike to school for random samples of 36 and of 900 students. Which plot shows the samples of 36?

   • Plot B: smaller samples spread wider.
   • Either one: the sample size does not change the spread.
   • Plot A: smaller samples land closer to the middle.
9. 9.

   100 dots from 62% to 68%. Plot B: 100 dots from 44% to 86%. Zee simulated percents who recycle for random samples of 20 and of 500 students. Which plot shows the samples of 500?

   • Plot A: bigger samples land closer to the middle.
   • Plot B: bigger samples spread wider.
   • Either one: the sample size does not change the spread.
10. 10.

    100 dots from 20% to 60%. Plot B: 100 dots from 35% to 45%. Ari simulated percents who bike to school for random samples of 16 and of 256 students. Which plot shows the samples of 16?

    • Plot A: smaller samples spread wider.
    • Plot B: smaller samples land closer to the middle.
    • Either one: the sample size does not change the spread.