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TWS 2: Planning and Carrying Out Investigations — Accuracy, Precision & Risk

5 min read 6 parts Lesson 2 of 8

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Lesson summary

TWS 2: Planning and Carrying Out Investigations — Accuracy, Precision & Risk — Alhussan International Academy — Science (Stages 7–9) notes: Plan an investigation by choosing equipment, a suitable range and enough readings, explain accuracy, precision and reliability, and write a …

  • Measuring variables
  • Controlling variables
  • Measuring cylinder
  • Combination
  • Reading a scale
  • Anomalous result

Part 1 of 6Making a plan

  • Purpose — a plan makes sure you have the equipment needed for useful results, forget no step and do nothing dangerous.
  • Aim — collect accurate and precise data to answer the scientific question.

Part 2 of 6Choosing equipment

  • Measuring variablesselect equipment that measures the independent and dependent variables.
  • Controlling variablesequipment may also be needed to control the other variables.
  • Choicesdecide which equipment is most appropriate and how to use it, such as whether a measuring cylinder or a beaker is better for volume and how to measure length accurately.
  • Measuring cylinderit measures smaller differences in volume than a beaker.

Part 3 of 6Accurate, precise and reliable data

WordMeaning
AccurateClose to the true value of what is being measured
PreciseRepeat measurements give similar results, grouped closely together
ReliableTrustworthy because enough measurements were taken
  • Precisionit is also determined by the smallest division of the measuring instrument.
  • Combinationreadings can be precise but not accurate, or accurate on average but not precise.
  • Reading a scalelook straight at the scale to make an accurate measurement.

Part 4 of 6Range and number of readings

  • Range = the difference between the biggest and smallest values of the independent variable.
    • If the range is too small, you may not be confident in your conclusion afterwards.
  • Repeats — usually three repeat measurements are made for every value of the independent variable, but fewer or more can be used.
  • Anomalous result = a measurement very different from the others in a set of repeats, which might be a mistake and must be dealt with.

Part 5 of 6Risk assessments

  • Purposeit explains how to reduce the chances of damage to equipment and injury to people.
  • Riskit depends on the probability of damage or injury happening and the consequence if it did.
  • Reducing probabilityfor example, keep glass objects away from the edge of the desk.
  • Reducing consequencefor example, wear safety goggles.
  • Small risksnote them and say they are not significant when writing the plan.
  • Hazard symbolsknow their meaning and consider them when planning.

Part 6 of 6What a plan includes

  • Fair test plan:
    • the scientific question and why a fair test was chosen;
    • the independent and dependent variables;
    • the control variables, how they are controlled and their values;
    • the hypothesis (the scientific reason for the conclusion) and the prediction;
    • the equipment list and how it is used step by step to collect accurate, precise data;
    • how results are recorded and a risk assessment, even if the risk is very low.
  • Other investigations — field studies, observations or secondary data need the question, why this type was chosen, the hypothesis and prediction.
    • They also need how precise, reliable data or observations are collected, the sources of secondary information, the equipment if done personally and a risk assessment.
  • Secondary data — the information must be reliable and the observations accurate.

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