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Evidence Limitations vs Source Credibility in QCE Science

A student-friendly explanation of the difference between source credibility and evidence limitations in QCAA Biology, Chemistry and Physics research investigations.

Updated 2026-05-13 ยท 2 min read

Evidence limitations vs source credibility in QCE Science

In QCE Science research investigations, students often write a lot about whether a source is credible and not enough about whether the evidence actually answers the research question.

Both matter, but they are different.

Source credibility asks who made the evidence

Source credibility is about trust. You are asking whether the source is likely to be reliable.

Useful questions include:

  • Was it written by qualified researchers or a reputable organisation?
  • Is the publication current enough for the topic?
  • Are methods, data and references visible?
  • Is there a commercial or political reason the source might be biased?
  • Is it peer-reviewed or published by a scientific, university or government body?

This is useful, but it is only the starting point. A credible source can still be weak for your research question.

Evidence limitations ask how useful the data is

Evidence limitations are about fit. You are asking whether the actual data can support your conclusion.

Useful questions include:

  • Were the conditions similar to the context in your research question?
  • Was the independent variable isolated clearly?
  • Did the source measure the dependent variable you need, or only a related variable?
  • Was the sample size, number of trials or range of values wide enough?
  • Are there confounding variables that make the trend harder to interpret?
  • Does the evidence support the whole question or only one part?

This is usually where stronger evaluation happens.

Example: weak vs stronger evaluation

Weak evaluation:

"Source 1 is reliable because it is from a university and was published recently."

Stronger evaluation:

"Source 1 is credible because it was published by university researchers, but its usefulness is limited because the experiment tested a much higher temperature range than the conditions in the research question. This means the observed reaction-rate trend supports the general relationship but cannot be applied directly to the chosen classroom-temperature context."

The stronger version still talks about credibility, but it also explains how the limitation affects the conclusion.

How to write an evaluation paragraph

Use this structure:

  1. Identify the evidence.
  2. State what it supports.
  3. Identify the limitation.
  4. Explain how the limitation affects the conclusion.
  5. Link back to the research question.

This works for Chemistry IA3, Biology IA3 and Physics IA3 because the core problem is the same: the evidence must be judged against the question, not just described.

Sources