Plan and conduct valid, reproducible investigations — AC9S9I02

• Design a method that tests the stated question and controls important variables.
• Explain validity, reliability/reproducibility and sources of random/systematic error.
• Write a method another group could follow consistently.
• Build risk, ethics and cultural/heritage protocols into planning rather than adding them afterwards.

Know independent, dependent and controlled variables; basic laboratory safety; measurement units; and why repeated measurements can reveal variation.

Validity asks whether the investigation actually tests the intended relationship. If two important variables change together, causation becomes difficult to interpret. Reproducibility asks whether others can obtain compatible results using the described method. More repeats do not repair a fundamentally invalid design.

Errors should be anticipated. Random variation causes readings to scatter; systematic error shifts readings in a consistent direction. Risk controls reduce likelihood/severity of harm. Ethical requirements protect people, animals and environments. Work involving Country/Place, cultural heritage or community knowledge may require permission and respectful protocols; scientific curiosity does not override those responsibilities.

• More repeats make any experiment valid. Repeats improve confidence in consistency, not a confounded design.
• Error means someone made a mistake. Measurement uncertainty and variation are normal features of data.
• Safety is a form completed after writing the method. Controls must shape the method.
• Permission is unnecessary if the purpose is scientific. Ethics and cultural protocols constrain acceptable methods.

1. Identify the confounding variable in a supplied method.
2. Rewrite one vague step so another group could reproduce it.
3. Classify a zero-offset balance as systematic error and reaction-time variation as random error.
4. Add one risk control and one ethical/environmental consideration to a field investigation.

1. List variables for a reaction-rate investigation.
2. Write a six-step reproducible method.
3. Identify two likely error sources and their likely effect.
4. Explain why three repeats cannot fix a poor control variable.
5. Create a risk-control table for one investigation.
6. Explain when permissions or cultural/heritage protocols may change a sampling plan.

Three groups test the same question. Group A controls variables but performs one trial; B performs ten trials but changes two variables; C controls variables, repeats five times and uses a poorly calibrated sensor. Rank the designs for different purposes and identify the highest-priority improvement for each.

1. What makes an investigation valid? Its design isolates/tests the intended relationship closely enough to answer the question.
2. What makes it reproducible? Methods are clear and conditions/data collection are sufficiently specified for others to repeat.
3. What is a systematic error? A consistent bias that shifts measurements in one direction.
4. Why include ethics/protocols? Valid science must also be conducted responsibly and with appropriate permissions.

1. Critique an investigation in which two variables change together.
   Name the validity problem and propose a precise control.
2. Explain how repeats, calibration and a clear method affect evidence quality differently.
   Do not claim they solve the same problem.
3. Redesign a field investigation to address risk, environmental ethics and relevant cultural protocols.
   Show how the method itself changes, not just a warning added at the end.

• I can diagnose validity problems.
• I can write reproducible steps.
• I distinguish random and systematic error.
• I integrate risk, ethics and protocols into design.

Exit ticket: Why can a highly repeatable experiment still be invalid?

Australian Curriculum v9.0 — AC9S9I02: valid, reproducible investigations including error, risk, ethics and relevant cultural protocols.

Victoria Levels 9–10 — VC2S10I02: Exact.

NSW Stage 5 — SC5-WS-03 and SC5-WS-04: Exact designs and conducts safe, ethical, valid and reliable investigations.

• AC9S9I01 questions/hypotheses
• AC9S9I03 precise data
• AC9S9I06 evaluation

• Australian Curriculum v9.0
• Victorian Curriculum F–10 Version 2.0
• NSW Science 7–10 Syllabus (2023)

Curriculum equivalents for Plan and conduct valid, reproducible investigations to answer questions and...

Mapped skill: plan and conduct valid, reproducible investigations to answer questions and test hypotheses, including identifying and controlling for possible sources of error and, as appropriate, developing and following risk assessments, considering ethical issues, and addressing key considerations regarding heritage sites and artefacts on Country/Place

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.

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.