Working Scientifically
What's covered
Key facts
A control experiment is an identical experiment run without the independent variable, used for comparison.
An anomalous result is a point that does not follow the trend of the other points.
Percentage change = (change ÷ original value) × 100.
Accuracy describes how close a measured value is to the true value.
Control variables are the variables kept the same throughout the experiment.
A categoric (label) variable such as colour is plotted as a bar chart; a continuous (numerical) variable such as wavelength is plotted as a line graph.
The range of a dataset is the largest value minus the smallest value; for 12, 15, 11, 19, 13 the range is 19 − 11 = 8.
A balance that always reads 0.5 g too high is a systematic error — all readings are shifted by the same amount.
The dependent variable is the variable that is measured as the outcome of the experiment.
A directly proportional relationship shows as a straight line passing through the origin.
Sample questions
A taste of the 71 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What best describes a scientific hypothesis?
- ✓A proposed explanation that leads to testable predictions
- •A random guess made before any observations are taken
- •A specific result that is certain to occur in any experiment
- •A well-tested explanation supported by much existing evidence
What is the independent variable in an experiment?
- •the variable kept constant throughout
- •the variable most likely to produce error
- ✓the variable you deliberately change
- •the variable you measure as the outcome
What is a line of best fit?
- •A line drawn through only the first and last data points
- •A line joining every data point in order
- ✓A line or curve passing as close as possible to all points
- •A line that passes through the origin only
What is 0.08462 rounded to 2 significant figures?
- •0.08
- •0.084
- •0.0846
- ✓0.085
In the AQA glossary, when is a measurement result considered accurate?
- ✓When it is judged to be close to the true value
- •When the instrument can detect very small changes
- •When the same person repeats it and gets the same result
- •When there is little spread about the mean value
What is a random error?
- •a consistent shift in all readings caused by faulty equipment
- •a mistake that only affects the first measurement in a series
- •an error resulting from misreading the scale on an instrument
- ✓unpredictable variation affecting results differently each time
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