Science · Grades 7–12
Measurements, uncertainty and fair comparisons · revision notes
A measurement combines a numerical estimate with units and an appropriate description of uncertainty. More digits do not necessarily mean better evidence.
Key ideas and conditions
Measurement
A measurement combines a numerical estimate with units and an appropriate description of uncertainty. More digits do not necessarily mean better evidence.
Repeats
Repeated observations can reveal variation. Repetition alone does not remove a consistent calibration error.
Comparisons
Change one factor at a time when suitable, or use a design that can separate multiple effects. Keep relevant conditions and definitions clear.
Conclusions
State what the data support, distinguish correlation from causation, and avoid extending a small test to every possible setting.
Explain without looking
- Give one way to separate random variation from a suspected systematic error.
- An instrument reads 0.2 units too high on each trial. What correction should be added to each reading?
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