Key Stage 3 science · Working scientifically

KS3 scientific attitudes: accuracy, evidence and risk

Scientific attitudes are the habits that make science trustworthy: reporting what you actually found rather than what you hoped for, caring about accuracy, accepting that explanations change when new evidence arrives, and weighing up risks sensibly. In Key Stage 3 these habits are taught through biology, chemistry and physics lessons rather than as a separate subject, and they underpin the practical work and evaluation questions pupils meet later at GCSE.

Scientific attitudes, explained

Teachers use the phrase “working scientifically” for the skills and attitudes that sit alongside the facts. At Key Stage 3 they are never taught in a vacuum: a pupil learns about being objective while investigating, say, how fast a solid dissolves or how far a spring stretches. Being objective means letting the evidence decide, not your hopes. If your prediction was that the heavier ball would fall faster and the timings say otherwise, the timings win, and you write down what you saw.

Pupils are also expected to use four words precisely, because in everyday speech they blur together. Accuracy is how close a measurement is to the true value. Precision is how closely repeated measurements agree with each other. A result is repeatable if the same person, using the same method and equipment, gets about the same answer again. It is reproducible if someone else, perhaps with different equipment, gets about the same answer too. Results that are both repeatable and reproducible are the ones scientists trust.

Science is not a list of fixed facts. Explanations are modified, and sometimes replaced, as better evidence and new ideas appear. Schools choose their own historical examples, for instance how the picture of the atom changed over time, how ideas about what causes disease developed, or how the movement of the Earth’s continents was first doubted and later accepted. Pupils also learn why results are published: so other scientists can check them. Peer review means independent experts examine the methods and reasoning before a report is published, and other scientists can then try to repeat the work.

The last strand is evaluating risks. A hazard is anything that could cause harm, such as hot water, a sharp edge or a trailing cable. The risk is how likely the harm is and how serious it would be. Pupils learn to write a short risk assessment: name the hazard, say who could be harmed and how, and describe the sensible precaution, such as wearing eye protection or tying back long hair. The same thinking helps them read news stories about risk with a healthy amount of questioning.

Words your child will hear

Objective: Based on the evidence rather than on opinion, hopes or what you expected to see.
Accuracy: How close a measurement is to the true value.
Precision: How close repeated measurements are to each other, whether or not they are correct.
Repeatable: The same person, with the same method and equipment, gets the same result again.
Reproducible: Different people, or different equipment, get the same result using the same method.
Peer review: Independent experts check a report’s methods and conclusions before it is published.
Hazard and risk: A hazard is something that could cause harm. The risk is how likely the harm is and how serious it would be.

What the National Curriculum says

In Key Stage 3, pupils should be taught to:

Pay attention to objectivity and concern for accuracy, precision, repeatability and reproducibility
Understand that scientific methods and theories develop as earlier explanations are modified to take account of new evidence and ideas, together with the importance of publishing results and peer review
Evaluate risks

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

Try it: judging three balances

A class weighs a standard mass that is known to be exactly 50.0 g, three times on each of three balances. Balance A reads 50.1 g, 49.9 g and 50.0 g. Balance B reads 52.3 g, 52.4 g and 52.3 g. Balance C reads 48.0 g, 51.5 g and 50.9 g. Which balance is accurate, and which is precise?

Start with the true value, 50.0 g, and find each mean. Balance A: (50.1 + 49.9 + 50.0) ÷ 3 = 50.0 g. Balance B: (52.3 + 52.4 + 52.3) ÷ 3 = 52.3 g. Balance C: (48.0 + 51.5 + 50.9) ÷ 3 = 50.1 g.
Balance A: the readings are within 0.1 g of the true value and of each other. It is both accurate and precise.
Balance B: the readings agree with each other to within 0.1 g, so it is very precise. But every reading is about 2.3 g too high (mean 52.3 g against a true value of 50.0 g), so it is not accurate. A constant shift like this points to a systematic problem, such as a balance that was not set to zero.
Balance C: the readings are spread over 3.5 g, so it is not precise. The mean happens to land near 50.0 g, but that is luck. You could not trust any single reading from this balance.
Now think about trust. If the same pupil got the same Balance A readings on another day, the result is repeatable. If a different pupil using a different balance also got about 50.0 g, it is reproducible. Balance B’s fault could be found by checking its zero with nothing on it and by comparing it with another balance.

Balance A is accurate and precise. Balance B is precise but not accurate (a consistent error of about 2.3 g). Balance C is not precise, and its accurate-looking mean cannot be relied on.

Common mistakes and how to help

Using “accurate” and “precise” to mean the same thing

In everyday speech both just mean “good”. In science they describe different things, and a very precise instrument can still be consistently wrong.

What helps: Use a target picture: darts tightly grouped but far from the bullseye are precise, not accurate. Ask “close to what?” each time one of the words is used.

Believing a good result is one that matches the prediction

Pupils often feel an experiment has “gone wrong” if the data disagree with what they expected, and are tempted to adjust or leave out readings.

What helps: Praise honest reporting. A surprising result is useful evidence: it may mean the prediction needs rethinking or the method needs improving, and both are real science.

Thinking that if scientific ideas change, science must be unreliable

Words like “just a theory” and headlines about scientists changing their minds suggest that nothing is settled.

What helps: Explain that ideas are refined, not thrown away at random. A new explanation has to account for everything the old one did, plus the new evidence.

Treating a hazard and a risk as the same, so anything with a warning sign is “too dangerous”

Pupils see the symbol and stop thinking. Every hazard carries a risk that depends on how it is used, and the risk can often be reduced a lot.

What helps: Ask three questions: what could go wrong, how likely is it, and what would we do to make it less likely or less serious?

How to help at home

Ask “how do we know?”. When a claim comes up, whether it is on a food packet, in a video or in a news story, ask what the evidence is and who checked it. Treat it as curiosity, not as an argument to win.
Measure the same thing three times. Measure the height of a door three times, or weigh an unopened bag of sugar whose label gives its mass, and compare the readings. Then try a different tape measure or set of kitchen scales. How close are the readings to each other (precision), how close is the bag to its label (accuracy), and does the second instrument agree (reproducibility)? No special equipment is needed.
Do a family risk talk. Before a bike ride, a recipe or a DIY job, ask your teenager to name the hazards, say which risk matters most, and suggest a precaution. Let them decide where possible, and talk afterwards about whether the precaution was sensible or more than was needed.
Follow an idea that changed. Pick one scientific idea, such as what causes disease or how continents move, and look up how people’s understanding changed and what evidence made the difference. A library book or a documentary is plenty.

Builds on

Years 5 and 6: Working scientifically

Leads on to

Key Stage 4: The development of scientific thinking
Key Stage 4: Experimental skills and strategies
Key Stage 4: Analysis and evaluation
Key Stage 4: Units, symbols and nomenclature