Correlation and causation
Ice-cream sales and sunburn cases both rise in summer, but ice-cream does not cause sunburn. Stronger sunlight and hotter weather influence both, so the pattern alone does not establish causation.
Year 8 Science • Science inquiry • Questioning and predicting • AC9S8I01
Good investigations begin with questions that evidence can answer. Patterns and models support reasoned predictions and testable hypotheses—not guesses.
Recall that observations describe what is detected, inferences interpret observations, and scientific models represent selected features or relationships.
Use the chain pattern or model → investigable question → variables → reasoned prediction or hypothesis → evidence. An investigable question names measurable variables and conditions. Questions such as “Should we…?” or “Is this good?” involve values and cannot be answered by experimental measurements alone.
A correlation means variables change together; causation means changing one produces a change in the other. Controlled investigations help test causation, while a confounding variable provides another possible explanation.
A prediction states an expected outcome. A hypothesis proposes a testable, directional relationship and a reason: If [independent variable changes], then [dependent variable changes], because [scientific reason].
A model may be a diagram, physical object, mathematical relationship or simulation. It can generate questions and predictions even though it simplifies reality; its predictions must still be compared with evidence.
Ice-cream sales and sunburn cases both rise in summer, but ice-cream does not cause sunburn. Stronger sunlight and hotter weather influence both, so the pattern alone does not establish causation.
Replace “Why do plants hate salt?” with “How does salt concentration affect the mass of potato tissue after 30 minutes?” Salt concentration is the independent variable and mass change is the dependent variable.
A plate-boundary model can support the question “How does boundary type affect earthquake and volcano patterns?” The model predicts a relationship that mapped observations can test.
If reactant concentration increases, reaction rate should increase because more particles in a given volume increase collision frequency. If light exposure increases within suitable limits, plant growth should increase because light supports photosynthesis.
Two explanations predict different outcomes when water temperature changes. Design one measurable question and hypothesis that could distinguish the explanations, then identify a confounding variable to control.
Exit ticket: Why can a strong correlation still fail to show causation?
Move from weak questions to measurable versions, then ask students to name variables and the scientific reason before planning a method.
Use everyday patterns and ask: What changes, what can we measure, and what else might explain the pattern?
Australian Curriculum v9.0 — AC9S8I01: develop investigable questions, reasoned predictions and hypotheses to explore scientific models, identify patterns and test relationships.
Victorian Curriculum F–10 Version 2.0 — Levels 7–8, VC2S8I01: Exact.
NSW Science 7–10 Syllabus (2023) — Stage 4, SC4-WS-02: Exact — the NSW Working Scientifically outcome directly align with the core inquiry process.
Broad international closest-topic links include NGSS Practice 1, KS3 Working Scientifically, Ontario Grade 8 STEM investigation skills, New Zealand investigating in science and middle-school NCERT inquiry. These are supportive comparisons, not identical curriculum structures.
| Framework | Level/Stage | Relationship | Mapping |
|---|---|---|---|
| Australian Curriculum | Year 8 | Canonical | AC9S8I01 |
| Victoria V2.0 | Levels 7–8 | Exact | VC2S8I01 |
| NSW 2023 | Stage 4 | Exact | SC4-WS-02 |
The SkillrHub lesson remains the primary learning resource. This optional video reinforces the explanation; you can complete the lesson and practice without watching.
Before you watch:
Amoeba Sisters — Develop a testable question and a reasoned hypothesis while recognising that science uses more than one fixed method.
As you watch: What makes a question testable using observations or measurements?
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Try it: Turn a question about seed germination into a testable question. Identify the variable you would change, what you would measure and the reason for your prediction.
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Mapped skill: develop investigable questions, reasoned predictions and hypotheses to explore scientific models, identify patterns and test relationships
These references identify matching or closely related learning. Curriculum sequence, terminology and depth vary, so teachers should use the mapped skill and lesson difficulty to confirm suitability.
| Region | Curriculum framework | Closest level or code |
|---|---|---|
| Australia | Australian Curriculum v9.0 | AC9S8I01 · Year 8 |
| Victoria | Victorian Curriculum F–10 Version 2.0 — Science | VC2S8I01 · Levels 7–8 |
| New South Wales | NSW Science 7–10 Syllabus (2023) | SC4-WS-02 · Stage 4 |
| United States (USA) | Next Generation Science Standards (NGSS) | Middle School (Grades 6–8) |
| Canada (Ontario) | Ontario Curriculum — Science | Grade 8 |
| United Kingdom (England) | National Curriculum in England — Science | Year 9, Key Stage 3 |
| India | NCERT / CBSE — Science | Class 8 |
Australian Curriculum v9.0 is the canonical source for this SkillrHub lesson. Victoria and NSW entries name the closest published state codes or outcomes; international entries are planning references rather than claims of identical curricula.
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Topic reference: AC9S8I01 — Investigable Questions, Predictions and Hypotheses — AC9S8I01
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