NCEA Level 1Evaluating informationAS 91946

Evaluating information: 7 exam questions solved step by step

What this lesson covers

  • Information is only as good as the data, the sample and the display behind it.
  • A strong response weighs the evidence, names its limitations and can bring in a personal view.
Key idea

7 claims, one checklist

  • 1. Redo the arithmetic.
  • 2. Sample: how many, how chosen?
  • 3. Relative or absolute? Link or cause?
  • 4. Judge it, with reasons.
Your turn

Question 1 · Achieved

  • Newsletter headline: "Two thirds of
  • students want a later start."
  • Survey: 360 of the 600 students said yes.
  • Is the headline accurate?
Worked example

Q1: is it two thirds?

  • Work out the percentage.
  • Compare with the claim.
  1. 360 ÷ 600 = 0.6part ÷ whole
  2. 0.6 × 100 = 60%
  3. 2 ÷ 3 × 100 ≈ 66.7%two thirds as a %
  4. 600 ÷ 3 × 2 = 400 studentstwo thirds of 600
  5. 400 − 360 = 40 students short
  6. Not accurate: 60% is 3 in 5
Your turn

Question 2 · Achieved

  • Advert for FizzUp, a made-up drink:
  • "4 out of 5 Kiwi teens prefer FizzUp!"
  • Small print: 20 of 25 teens asked
  • at the FizzUp stand at a festival.
Worked example

Q2: 4 out of 5 teens?

  • Is the maths right?
  • Then judge the sample.
  1. 20 ÷ 25 = 0.8 = 80%
  2. 4 ÷ 5 = 0.8 = 80%
  3. only 25 teensvery small sample
  4. asked at the FizzUp standbiased: likely fans
  5. one festival, not all NZ teens
  6. Maths right, evidence poor
Your turn

Question 3 · Merit

  • Headline: "Late buses up 50%!"
  • The council checked 2,000 trips a year.
  • Late: 80 last year, 120 this year.
  • Is 50% true? Is it fair?
Worked example

Q3: late buses up 50%?

  • Relative: ÷ last year.
  • Absolute: the real gap.
  1. 120 − 80 = 40 more late trips
  2. 40 ÷ 80 = 0.5 = 50%relative change
  3. last year: 80 ÷ 2,000 = 4%
  4. this year: 120 ÷ 2,000 = 6%
  5. 6 − 4 = 2 percentage pointsabsolute change
  6. 100 − 6 = 94% still on time
  7. True, but only 4% to 6%
Your turn

Question 4 · Merit

  • Study of 120 students. Scored over 60%:
  • 56 of 80 who eat breakfast,
  • 20 of 40 who skip it.
  • Headline: "Breakfast boosts marks."
Worked example

Q4: does breakfast boost marks?

  • Compare percentages.
  • A link is not a cause.
  1. breakfast: 56 ÷ 80 = 70%
  2. skip: 20 ÷ 40 = 50%
  3. 70 − 50 = 20 percentage points
  4. breakfast causes the marksonly observed
  5. other factors: sleep, routine
  6. A link here, not proof of cause
Your turn

Question 5 · Merit, in context

  • Radio station website poll: "Should
  • the new cycleway be removed?"
  • 1,020 of 1,200 votes: yes.
  • Station: "85% of the town want it gone."
  • Careful: is a big sample enough?
Worked example

Q5: an online poll

  • Who chose to vote?
  • Size does not fix bias.
  1. 1,020 ÷ 1,200 = 0.85 = 85%
  2. self-selected: chose to vote
  3. strong views more likely to vote
  4. listeners, not the whole town
  5. one person, several votes?
  6. "1,200 votes, so it is fair"big but still biased
  7. Not reliable for the whole town
Your turn

Question 6 · Excellence

  • StudyPal (a made-up app) advert:
  • "Users improved by 12 marks on average!"
  • 30 volunteers: mean 54 before the term,
  • 66 after. No other group was tested.
Worked example

Q6: check, then the design

  • Check the arithmetic.
  • Then the design.
  1. 66 − 54 = 12 marks
  2. 12 ÷ 54 × 100 ≈ 22.2%relative rise
  3. only 30 studentssmall sample
  4. volunteers chose to joinlikely keener
  5. no comparison groupwould they improve anyway?
Worked example

Q6: the judgement

  • Who made the claim?
  • Judge, with reasons.
  1. no comparison group
  2. source: the company itselfreason to oversell
  3. fairer: two random groups
  4. compare the two improvements
  5. Rise real, cause not shown
Your turn

Question 7 · Excellence

  • Headline: "Teen screen time up 25%.
  • Phones are ruining teen sleep."
  • The two surveys behind it are shown.
SurveyTeensScreensSleep
2024500, across NZ4 h a day8 h a night
202650, one school5 h a day7.5 h a night
Worked example

Q7: check, then the samples

  • Check both changes.
  • Compare the samples.
  1. screens: 5 − 4 = 1 hour more
  2. 1 ÷ 4 = 0.25 = 25%relative change
  3. sleep: 8 − 7.5 = 0.5 h = 30 min
  4. 0.5 ÷ 8 × 100 = 6.25%relative change
  5. NZ-wide 500, one school 50
  6. not a fair comparisondifferent populations
Worked example

Q7: the judgement

  • A link is not a cause.
  • Judge, with your view.
  1. not a fair comparison
  2. both changed: a link at most
  3. other causes: homework, jobs
  4. "phones are ruining sleep"not shown by this data
  5. better: random sample, same way
  6. my view: worth a proper study
  7. Weak evidence: not supported
Summary

The checklist that answered all seven

  • Check the numbers, then the sample, then the claim.
StepHow
Numbersredo the arithmetic yourself
Samplehow many, and who chose them
Biasself-selected, or a seller
Changegive relative and absolute
Linka link is not a cause
Judgementverdict, reasons, your view

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