Skip to content
HSCScienceModule 1 pilotSources and coverage
Investigating Science · Year 11 · Lesson 8 of 12

Planning a safe, valid method

How does primary data provide evidence for further investigation?

30–45 min suggested learning

Module 1 pilot only. This learning resource supports the 2017 syllabus and complements your school’s supervised practical program.

Think first and set your goal

Think First

Could another group follow your instructions without asking you what “drop it normally” means?

Saved on this device

Learning Intentions

  • Write an operational method with repeated measurements.
  • Match safety actions to actual hazards.
  • Explain how planning supports validity and reliability.

Key Terms

validity
How well the method addresses the intended question while managing relevant alternative influences.
reliability
Dependability of results, considered through consistent methods and evidence of repeatability.
hazard
A source of possible harm; risk also depends on likelihood and consequence.

Three printable worksheets

BuildPrintable questions and teacher keyApplyPrintable questions and teacher keyEvaluatePrintable questions and teacher key

A usable method is a set of decisions

A usable method is a set of decisions

A method should specify values of the independent variable, how the response is measured, controls, repeats and recording rules. For a paper spinner, define wing dimensions, release height, timing start and end, and trial order. “Repeat several times” should become a specified number of trials per condition.

A second group should be able to reproduce the important conditions without guessing. Record practical tolerances: a nominal 1.5 m release height may be set using a marked wall reference. If a spinner hits furniture, record the event and apply a predefined invalid-trial rule rather than quietly selecting the best result.

Book notes: A usable method is a set of decisions

A method should specify values of the independent variable, how the response is measured, controls, repeats and recording rules. For a paper spinner, define wing dimensions, release height, timing start and end, and trial order. “Repeat several times” should become a specified number of trials per condition.

Saved on this device

Which instruction is most operational?

Plan safety around the real activity

Plan safety around the real activity

Use an accessible low release height; no climbing on chairs or throwing objects. Keep a clear drop zone, use scissors under school procedures and choose light paper models without sharp attachments. Consider people, equipment and the environment. A general “be careful” does not specify a risk-reduction action.

For practical alternatives involving warm water, plants or field observations, teachers must approve conditions and local procedures. This pilot does not require flames, microbial cultures, tasting substances or unsafe heights. A source-analysis task can teach those phenomena without recreating avoidable hazards.

Book notes: Plan safety around the real activity

Use an accessible low release height; no climbing on chairs or throwing objects. Keep a clear drop zone, use scissors under school procedures and choose light paper models without sharp attachments. Consider people, equipment and the environment. A general “be careful” does not specify a risk-reduction action.

Saved on this device

What is the main purpose of repeated trials?

Separate control, repetition and improvement

Separate control, repetition and improvement

Relevant controls improve validity by reducing competing explanations. Repeated trials provide information about variation and help assess reliability. Calibration and a clear endpoint improve measurement quality. None of these makes a result certain, and repeating a systematically flawed method may produce consistent but wrong readings.

Pilot the method before collecting the main dataset. If timing is too variable, replace hand timing with suitable video or an approved sensor, or choose a longer measurable interval. Record the method revision. The strongest improvement targets an identified limitation rather than adding technology without a reason.

Book notes: Separate control, repetition and improvement

Relevant controls improve validity by reducing competing explanations. Repeated trials provide information about variation and help assess reliability. Calibration and a clear endpoint improve measurement quality. None of these makes a result certain, and repeating a systematically flawed method may produce consistent but wrong readings.

Saved on this device

Which safety control fits a paper-spinner height measurement?

Worked example

Worked example: Improve “Drop each spinner and write its time; do it again.”

  1. Build three wing lengths using the same paper and folding rule.
  2. Release from a marked 1.5 m height over a clear floor, without climbing.
  3. Define timing from release to first floor contact and record seconds.
  4. Collect five trials per length in randomised order; record collisions and apply the stated re-trial rule.

The method specifies changed values, measurement endpoints, controls, repeats and safe implementation.

Independent practice

Five questions from this lesson’s eight-question bank

Answer the five-question Quick Check. Use the feedback to repair an idea before retrying.

Short answer

Explain and evaluate

Q1. Write four essential method details for a paper-spinner investigation.

Saved on this device
Explain and evaluate

Q2. Distinguish validity and reliability using the spinner investigation.

Saved on this device
Explain and evaluate

Q3. Give a limitation and an improvement that directly addresses it.

Saved on this device
Answers and model responses

Activities

Activity 1

Hazard: sharp scissor blades; risk: cuts during cutting/handling; control: school-approved scissors and cutting procedure, pass safely and keep hands clear. Assess using the school’s risk framework.

Activity 2

They reveal variation between trials and support a repeatability estimate. They do not remove a fixed timer delay, confounded paper types or an inconsistent release-height comparison.

Short Answer Model Answers

Q1: Specify wing-length values; paper/folding/release controls; defined start/end timing in seconds; repeats and trial order. Include reachable height and clear drop zone.

Q2: Validity concerns whether the length comparison addresses length rather than changing paper or height. Reliability concerns dependable repeated measurements and variation under consistent methods. Repeats alone do not ensure validity.

Q3: Hand reaction time contributes timing scatter; suitable high-frame-rate video with defined release/contact frames can reduce that limitation. Accept a specific limitation and matched feasible improvement.