CAEC Science Preparation Course: Inquiry: error, reliability and conclusions

1. Pregunta 1 de 16

   In science, what does it mean if results are reliable?

   • AThe results were shared online and many people liked them
   • BThe results match what the scientist hoped to find
   • CRepeated tests give similar results
   • DThe test was done only once, but very slowly and carefully
   Ver respuesta

   Respuesta: C. Repeated tests give similar results

   Reliability is about consistency: repeating the test should give similar results.

2. Pregunta 2 de 16

   What does it mean if an investigation is valid?

   • AIt was carried out by a famous scientist at a large university
   • BIts results were surprising and made the news headlines
   • CIt used the newest and most expensive equipment available
   • DIt really measures what it claims to
   Ver respuesta

   Respuesta: D. It really measures what it claims to

   A valid test measures the right thing in a fair way, with other variables controlled.

3. Pregunta 3 de 16

   Which trial is most likely an error and should be checked?

   Trial	1	2	3	4
   Reaction time (s)	0.31	0.29	0.30	0.52

   • ATrial 2
   • BTrial 3
   • CTrial 4
   • DTrial 1
   Ver respuesta

   Respuesta: C. Trial 4

   Trials 1–3 are all close to 0.30 s. Trial 4 (0.52 s) is far from the others, so it is an outlier, perhaps caused by a distraction.

4. Pregunta 4 de 16

   A kitchen scale shows 2 g even when nothing is on it. Every mass measured on it will be 2 g too high. What kind of error is this?

   • ARandom error
   • BSystematic error
   • CSelective reporting
   • DA controlled variable
   Ver respuesta

   Respuesta: B. Systematic error

   A systematic error pushes every measurement the same way by the same amount. Zeroing (taring) the scale fixes it.

5. Pregunta 5 de 16

   Different students start and stop a stopwatch slightly early or late each time. What is the best way to reduce this kind of error?

   • AStop recording times and estimate them instead
   • BKeep only the fastest time and ignore the rest
   • CUse a bigger stopwatch with a larger screen
   • DRepeat the timing and use the average
   Ver respuesta

   Respuesta: D. Repeat the timing and use the average

   Human reaction time causes random error. Repeating trials and averaging reduces its effect.

6. Pregunta 6 de 16

   Which conclusion is supported by the data?

   Each jar started with 300 mL of water at 80 °C. All jars were the same size and sat on the same table for 30 minutes.

   Wrap around jar	Water temperature after 30 min (°C)
   No wrap	52
   Aluminum foil	58
   Newspaper	61
   Wool sock	67

   • AAluminum foil is the best insulator for every possible use
   • BThe newspaper wrap added heat to the water in its jar
   • CAll four wraps kept the water warm equally well
   • DIn this test, the wool sock kept the water warmest
   Ver respuesta

   Respuesta: D. In this test, the wool sock kept the water warmest

   The wool-wrapped jar stayed warmest (67 °C). The data is about this test only, so broad claims like "every use" go too far.

7. Pregunta 7 de 16

   How many degrees did the water with no wrap cool down in 30 minutes?

   Each jar started with 300 mL of water at 80 °C. All jars were the same size and sat on the same table for 30 minutes.

   Wrap around jar	Water temperature after 30 min (°C)
   No wrap	52
   Aluminum foil	58
   Newspaper	61
   Wool sock	67

   • A52 °C
   • B22 °C
   • C13 °C
   • D28 °C
   Ver respuesta

   Respuesta: D. 28 °C

   It started at 80 °C and ended at 52 °C: 80 − 52 = 28 °C.

8. Pregunta 8 de 16

   You want to keep soup hot in a jar for a field trip. How can you best apply the results of this investigation?

   Each jar started with 300 mL of water at 80 °C. All jars were the same size and sat on the same table for 30 minutes.

   Wrap around jar	Water temperature after 30 min (°C)
   No wrap	52
   Aluminum foil	58
   Newspaper	61
   Wool sock	67

   • APut the jar in a newspaper bag and leave the lid off
   • BWrap the jar in a wool sock
   • CWrap the jar in foil because it is shiny
   • DLeave the jar unwrapped
   Ver respuesta

   Respuesta: B. Wrap the jar in a wool sock

   The investigation showed wool kept water hottest, so it is the best choice from the materials tested.

9. Pregunta 9 de 16

   Which study's results are more reliable and credible, and why?

   Study	People tested	How people were chosen	Published
   A	18	Volunteers who answered an online ad	Company website
   B	1,200	Chosen at random from several cities	Peer-reviewed journal

   • AStudy A, because it was posted online faster than Study B
   • BStudy B: large random sample, peer-reviewed
   • CBoth are equal, because both studies tested real people
   • DStudy A, because volunteers who answer ads are more honest
   Ver respuesta

   Respuesta: B. Study B: large random sample, peer-reviewed

   Study B used many people chosen at random and passed peer review. Study A had few self-selected volunteers and no independent check.

10. Pregunta 10 de 16

    A study found that towns with more ice cream sales also have more drownings. What is the best explanation?

    • AHot weather raises both; one need not cause the other
    • BEating ice cream causes people to drown while swimming
    • CDrowning accidents make people go out and buy ice cream
    • DThe data must have been made up, so ignore the study
    Ver respuesta

    Respuesta: A. Hot weather raises both; one need not cause the other

    Two things that change together are correlated, but that does not prove one causes the other. A third factor, hot weather, can explain both.

11. Pregunta 11 de 16

    A new hand cream helped the skin of 10 mice in one lab. The company says it "works for everyone." What is wrong with this claim?

    • AMice can never be used in any kind of science research
    • BHand creams are cosmetics, so they cannot be tested at all
    • CIt overgeneralizes from a small test on animals
    • DTen mice is far too many animals for a skin cream test
    Ver respuesta

    Respuesta: C. It overgeneralizes from a small test on animals

    A small test on mice does not show what will happen in all people. More testing in people is needed.

12. Pregunta 12 de 16

    A friend says, "My cousin drank celery juice and her cold went away, so celery juice cures colds." Why is this weak evidence?

    • ACelery juice was not measured in litres or millilitres
    • BColds are caused by viruses, which cannot be studied
    • CIt is one story with no comparison group
    • DYour friend is not a trained scientist with a degree
    Ver respuesta

    Respuesta: C. It is one story with no comparison group

    One personal story (an anecdote) has no control group. The cold might have ended without the juice.

13. Pregunta 13 de 16

    In an experiment on how temperature affects how fast sugar dissolves, a student stirred some cups but not others. How does this affect the results?

    • ALess valid: stirring was not controlled
    • BMore reliable, because stirring always helps sugar mix
    • CNo effect, because stirring is not related to temperature
    • DIt proves that stirring was the independent variable
    Ver respuesta

    Respuesta: A. Less valid: stirring was not controlled

    Stirring also speeds up dissolving. Because it was not kept the same, you cannot tell whether temperature or stirring caused the differences.

14. Pregunta 14 de 16

    A student found that seeds sprouted fastest at 25 °C out of the temperatures 5, 15 and 25 °C. What is a sensible next investigation?

    • AStop, because 25 °C must be the best temperature there is
    • BRepeat only the 5 °C test several more times
    • CTest temperatures above 25 °C
    • DChange the seed type and the temperature at the same time
    Ver respuesta

    Respuesta: C. Test temperatures above 25 °C

    The best temperature might be higher than 25 °C. Testing beyond the range, while changing one variable at a time, extends the conclusion.

15. Pregunta 15 de 16

    Which source is usually the most credible for a claim about a new medicine?

    • AAn advertisement from the company that sells the medicine
    • BA comment on a forum from an anonymous user who tried it
    • CA social media post that has thousands of likes and shares
    • DA peer-reviewed study by independent researchers
    Ver respuesta

    Respuesta: D. A peer-reviewed study by independent researchers

    Peer-reviewed research by independent scientists is checked by experts and less likely to be biased.

16. Pregunta 16 de 16

    A student measured the temperature of a cup of water once, with the bulb of the thermometer not fully in the water. What is the best way to improve the investigation?

    • AUse the same method but write the answer more neatly
    • BGuess the temperature by touching the water with a finger
    • CPut the bulb fully in the water and take several readings
    • DRound the reading to the nearest 10 °C to hide small errors
    Ver respuesta

    Respuesta: C. Put the bulb fully in the water and take several readings

    Using the tool correctly fixes a source of error, and repeated readings make the result more reliable.

Teclado: 1–4 para responder, Intro para la siguiente pregunta.

El examen real: 55% on each CAEC test