Judge a biology claim: evidence, reasoning and reliable sources

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   An ad says, "A gardener's tomato grew 40% bigger with our spray!" What is the biggest problem with this claim, Ari asks?

   • One plant, no comparison group, and the seller made the claim
   • The problem is that tomatoes are fruits
   • No problem, since a real gardener said it
   • No problem, since 40% is a big gain
2. 2.

   A survey found more frogs and more insects in gardens near a pond. Esme's friend claims the frogs attract the insects. What is the problem?

   • It is a link from a survey; the pond could explain both
   • Frogs attract insects, since both are higher
   • There were fewer frogs near the pond
   • Insects attract the frogs, which settles the question for good

3. Read this first

   Use this

   Two studies (invented examples). Study A: 10 plants, no control group, found that compost helped. Study B: 200 plants with a control group found no difference.

4. 3.

   Jun finds two compost studies that disagree. What is the best conclusion?

   • Throw out both studies, since studies that disagree are both wrong
   • Weigh B more, since it is larger and controlled, and test again
   • Average the two studies' numbers together
   • Trust A, since it found an effect
5. 4.

   A blog says mold grows faster in the fridge, based on one slice. Luz's class data on 20 slices show the opposite. Which should Luz trust?

   • The blog, since it is published online
   • The class data, since they use more slices and a clear comparison
   • The blog, since one clear slice is enough
   • Neither one, since mold grows far too randomly for anyone to study it

6. Mean height after 21 days (example data)

   Group	Plants	Mean height (cm)
   with plant food	10	21
   without plant food	10	15

7. 5.

   Milo's claim: "Plant food makes plants grow twice as tall." Which revised claim fits the data best?

   • Plant food helped these bean plants grow about 6 cm taller on average
   • Plant food makes any plant grow taller
   • Plant food doubles the height of bean plants
   • Plant food had no effect on height

8. Bean seeds sprouted by day 5, 20 seeds each (example data)

   Seeds	Sprouted
   soaked overnight	18
   not soaked	11

9. 6.

   Noah's claim: "Soaking makes seeds sprout." Which revised claim fits the data best?

   • By day 5, more soaked bean seeds had sprouted than unsoaked ones
   • Soaking makes any seed sprout within 5 days
   • Unsoaked seeds cannot sprout
   • Soaked seeds sprouted sooner because the water made them heavier

10. Bee visits to three flower patches, 30-minute count (example data)

    Patch	Visits
    purple	24
    yellow	15
    white	6

11. 7.

    Pia's claim: "Bees prefer purple because purple flowers have more nectar." Which revised claim fits the data best?

    • Bees visited white flowers most
    • In this count, bees visited purple flowers most; the reason was not tested
    • Bees avoid white flowers everywhere
    • Purple flowers have more nectar, so bees prefer them

12. Use this

    Two sources (invented examples). A: a shop page selling a plant spray shows 2 plants: sprayed 30 cm, unsprayed 20 cm. B: a university test of 60 plants found both groups averaged 22 cm.

13. 8.

    Ren compares a shop page and a university test of the same plant spray. Which conclusion is best?

    • The spray works, since the shop's photo clearly shows a taller sprayed plant
    • The larger test, from a source with nothing to sell, shows no effect
    • The two count equally, since both show plants
    • The spray works, since 30 cm beats 20 cm

14. Use this

    Two sources (invented examples). A: a government science page, reviewed in 2025, with references, says plants need light to make their food. B: an unsigned 2008 blog says plants given sugar water need no light.

15. 9.

    Tala finds two pages about what plants need. Which is more reliable, and why?

    • A, since it is dated, reviewed and backed by references
    • B, since it has been online longer
    • B, since its idea is more surprising and new than the government page
    • Neither, since both are websites

16. Use this

    Two sources (invented examples). A: a peer-reviewed study of 300 seeds found salt water lowered sprouting. B: a comment says, "My seeds sprouted fine in salty soil!"

17. 10.

    Zee reads a study and a comment about salt and seeds. Which should Zee trust more?

    • The comment, since it is a real person's own experience with salty soil
    • The study, since it tested many seeds and experts checked it
    • The comment, since one success disproves the study
    • Both equally, since each one has a point