Random samples from a known group

Answer Key - Grade 8 Math Worksheet

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

1. 1.

   Ari draws five samples of four from a bag with 9 blue of 10. The blue counts are in the figure. What percent of sampled draws were blue?

   85
2. 2.

   Bo draws five samples of four from a bag with 3 blue of 10. The blue counts are in the figure. What percent of sampled draws were blue?

   25
3. 3.

   Kira draws five samples of four from a bag with 7 blue of 10. The blue counts are in the figure. What percent of sampled draws were blue?

   65

4. Read this first

   Population dot plot

   9 blue, 1 yellow. Five sample dot plots, each four dots; blue counts: 3, 4, 4, 4, 4. Draw without looking; return all counters between samples.

5. 4.

   Milo draws five samples of four from a bag with 9 blue of 10. The blue counts are in the figure. What percent of sampled draws were blue?

   95

6. Population dot plot

   3 blue, 7 yellow. Five sample dot plots, each four dots; blue counts: 1, 0, 0, 3, 3. Draw without looking; return all counters between samples.

7. 5.

   Noah draws five samples of four from a bag with 3 blue of 10. The blue counts are in the figure. What percent of sampled draws were blue?

   35
8. 6.

   Pia draws five samples of four from a bag with 4 blue of 10. The blue counts are in the figure. What percent of sampled draws were blue?

   45

9. Population dot plot

   8 blue, 2 yellow. Five sample dot plots, each four dots; blue counts: 2, 3, 4, 4, 4. Draw without looking; return all counters between samples.

10. 7.

    Zee draws five samples of four from a bag with 8 blue of 10. The blue counts are in the figure. What percent of sampled draws were blue?

    85
11. 8.

    Ari compares a bag of 10 counters (4 blue). Plan A draws 5 without looking: 3 blue. Plan B handpicks 5: 2 blue. Which plan uses a fair method to sample the whole bag?

    • Plan B: its matching blue count proves the selection method was fair.
    • Neither plan, because a random sample must match the bag’s blue share exactly.
    • Plan A: drawing without looking gives every counter the same chance.
    • Plan B, because picking the blue counters by hand makes the sample representative.

12. Population dot plot

    6 blue and 4 yellow. Plan A sample: 2 blue of 5; Plan B sample: 3 blue of 5. All counters return before another draw.

13. 9.

    Bo compares a bag of 10 counters (6 blue). Plan A draws 5 without looking: 2 blue. Plan B handpicks 5: 3 blue. Which plan uses a fair method to sample the whole bag?

    • Neither plan, because a random sample must match the bag’s blue share exactly.
    • Plan B, because picking the blue counters by hand makes the sample representative.
    • Plan A: drawing without looking gives every counter the same chance.
    • Plan B: its matching blue count proves the selection method was fair.
14. 10.

    Esme compares a bag of 10 counters (8 blue). Plan A draws 5 without looking: 3 blue. Plan B handpicks 5: 4 blue. Which plan uses a fair method to sample the whole bag?

    • Plan B, because picking the blue counters by hand makes the sample representative.
    • Plan B: its matching blue count proves the selection method was fair.
    • Plan A: drawing without looking gives every counter the same chance.
    • Neither plan, because a random sample must match the bag’s blue share exactly.