QCAA assignments

Improvements vs Extensions in QCE Science Assignments

A clear guide to writing better improvements and extensions in QCAA student experiments and research investigations.

By Sylligence · Published 2026-05-06 · Updated 2026-07-17 · 3 min read

Improvements and extensions are not the same thing. Mixing them up can make your evaluation sound generic, even when your data analysis is good.

Improvements strengthen the same research question

An improvement should make the same investigation more valid, reliable or accurate.

Good improvements usually come directly from a limitation:

• If trial data was inconsistent, increase repeats or control the inconsistent condition.
• If the instrument was not precise enough, use a more precise measurement tool.
• If the current range cannot resolve the relationship asked by the same research question, test a wider but still relevant range.
• If temperature changed during the experiment, control temperature more carefully.
• If secondary evidence used different conditions, find or generate evidence under matching conditions.

The test is simple: would this change help answer the same research question better? If yes, it is probably an improvement.

A wider range is not automatically an improvement. It is an improvement when the existing range prevents a reliable conclusion to the same question. It becomes an extension when the added range deliberately investigates behaviour outside the question's current scope, such as a new regime, threshold or context.

Extensions investigate a related new question or scope

An extension moves beyond the current research question while staying connected to the broader claim or topic.

Examples:

• After answering a question within one concentration range, investigate a different range where a new mechanism or relationship may apply.
• After testing one species, material or fuel, compare a related species, material or fuel.
• After measuring one dependent variable, investigate a related outcome.
• After evaluating one part of a claim, investigate another factor that the claim depends on.

The test is different: does this create a new but related question? If yes, it is probably an extension.

Use purpose and scope, not the physical action

The same physical change can be classified differently:

| Proposed change | Improvement when… | Extension when… | | --- | --- | --- | | Wider variable range | the existing range is too narrow to answer the same RQ | the new range tests behaviour beyond the stated RQ | | More trials | they reduce uncertainty for the same conditions | they add a new population, context or condition | | New source | it fills an evidence gap in the same RQ | it answers a different part of the broader claim | | Different material | it is a necessary control for the same comparison | it creates a new comparison question |

Weak examples to avoid

Avoid writing:

• "Do more trials" without saying why more trials are needed.
• "Use better equipment" without naming the measurement issue.
• "Research more sources" without explaining what kind of evidence is missing.
• "Investigate other factors" without naming a specific factor and why it matters.

These sound like filler. Strong evaluation is specific.

A stronger sentence pattern

For improvements:

"Because [specific limitation] affected [validity/reliability/accuracy] by [effect on data], the investigation could be improved by [specific change]. This would strengthen the conclusion by [link to research question]."

For extensions:

"Because this investigation only considered [narrow focus], a useful extension would be to investigate [related new variable/context]. This would test whether the broader claim still holds when [new condition] is considered."

Related guides

• Apply the distinction in a Chemistry IA2 student experiment.
• Use it for secondary evidence in a Chemistry IA3 research investigation.
• Separate evidence limitations from source credibility.

Sources and methodology

• QCAA Chemistry IA2 sample assessment instrument
• QCAA Chemistry IA3 sample assessment instrument
• QCAA ISMG information