Surveys, experiments and observational studies, and judging a report

Answer Key - Grade 11 Math Worksheet - Challenge Me

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

1. 1.

   Zee reads a school newsletter reporting that 85% of students want a longer recess. The 160 replies came from readers who chose to mail back a form. What is its main problem?

   • Nothing: 160 replies is plenty, so the result fairly shows what the whole school wants.
   • Readers who chose to reply may care more; 160 replies cannot stand for the school.
   • 160 replies is too few to tell anything.
2. 2.

   Ari reads a report that 72% of the school's 1,800 students want a later start. The 240 answers came from an online poll anyone could answer. What is its main problem?

   • 240 answers is too few to tell anything.
   • Nothing: 240 answers is plenty, so the result fairly describes the whole school.
   • Students who chose to answer may feel strongly; 240 answers cannot stand for 1,800.
3. 3.

   Bo reads a report that compared the sleep and grades of 300 students: "Students who sleep more get better grades, so more sleep raises grades." What is its main problem?

   • 300 students is too few to tell anything about how sleep and grades are linked in school.
   • The groups were not assigned, so it shows a link, not that sleep raises grades.
   • Nothing: the link between them proves it.
4. 4.

   Jun's report graph of field-trip votes starts its axis at 45. The zoo got 60 and the museum 50. Using the counts, how many times as many votes did the zoo get?

   1.2
5. 5.

   Kira's report graph of lunch votes starts its axis at 55. Pizza got 75 and pasta 60. Using the counts, how many times as many votes did pizza get?

   1.25
6. 6.

   Milo's report graph of class-trip votes starts its axis at 70. The park got 90 and the library 75. How many times as tall does the park bar look?

   4
7. 7.

   Noah's club had 48 volunteers. Half were assigned at random to a typing game, half to plain practice; the game group typed faster. Which claim is honest?

   • The typing game makes every student type faster.
   • The game likely made these volunteers faster; it may not hold for all students.
   • It shows only a link, because the volunteers were not assigned to their two groups.
8. 8.

   Pia assigned 32 tomato plants from one garden bed at random to plant food or plain water; the plant-food group grew taller. Which claim is honest?

   • It shows only a link, because the plants were not assigned to plant food or to plain water.
   • Plant food likely helped these tomato plants; other plants may differ.
   • Plant food makes every plant grow taller.
9. 9.

   Ren surveyed 120 students drawn at random from all 900. Those who read daily tend to have higher spelling scores. Which claim is honest?

   • The link holds only for the 120 students asked.
   • Among the 900 students, daily readers tend to spell better; reading may not be the cause.
   • Reading daily makes the school's students spell better.
10. 10.

    Tala surveyed 150 students drawn at random from all 1,000. Those who play outside after school tend to sleep longer. Which claim is honest?

    • The link holds only for the 150 students asked.
    • Playing outside makes the school's students sleep longer.
    • Among the 1,000 students, outdoor players tend to sleep longer; playing may not be the cause.