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Year 9 English | Understand, justify, check

Separate an observed change from its proposed cause

A measured change can be real while its cause remains uncertain. When a report links an intervention to an outcome, examine what else changed and whether the comparison can isolate the claimed effect.

Read: The electricity comparison

A community hall replaced its old lights with efficient fittings. The next monthly electricity bill was 22% lower than the previous month, and a newsletter attributed the whole saving to the new lights. The later month included a two-week closure for floor repairs, while the earlier month had a full events calendar. No separate lighting meter was used. The manager described the lower bill as encouraging and proposed comparing months with similar opening hours before estimating the lighting savings.

You can reread this original passage while answering.

What to notice

Before and after describe timing. They do not, by themselves, prove causation. Occupancy, season, duration and measurement method may also affect a comparison.

What to do

Identify the observed result and the explanation attached to it. List another plausible influence, then ask what additional comparison would help distinguish the explanations.

Why it works

Testing alternative explanations strengthens an evaluation without requiring the reader to reject the reported measurement. It allows a proportionate conclusion: the result is consistent with a benefit, but may not establish its size or cause.

Work through an example

Does a lower electricity bill after a lighting change prove the new lights caused the entire saving?

  1. The bill records a reduction during the later period.
  2. The passage also identifies lower building use during that period.
  3. Both could affect electricity use, so the entire reduction cannot be confidently attributed to lighting alone.

A common mistake

Finding a weakness in a causal claim does not prove the intervention had no effect. The evidence may support uncertainty rather than the opposite conclusion.

A strategy to try

Use precise qualifiers in an evaluation. “The bill fell” reports an observation; “the lights caused the entire fall” is a stronger claim that needs additional support.

Try it now

Try three questions

No account is needed. These examples do not change saved learning progress. Choose an answer and check it for an explanation; you can try again.

1. Which detail most directly weakens attribution of the entire saving to the lights?
Help: a starting point

Look for another change between the two billing periods.

Help: the next step

Consider how that change could affect electricity use without any lighting improvement.

2. Which conclusion best fits the passage?
Help: a starting point

Separate the observed bill reduction from the newsletter’s causal explanation.

Help: the next step

Choose a conclusion that preserves the observation without overstating its cause.

3. Which follow-up would most directly improve the comparison?
Help: a starting point

Identify the factor that makes the two months difficult to compare.

Help: the next step

Choose a follow-up that makes that factor more similar or measures it explicitly.

For parents and carers

Ask the learner to preserve what the evidence does show while limiting what it does not. This is more demanding than labelling a report reliable or unreliable. The related statistics lesson explains why summaries must remain connected to their underlying data.

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