Learning outcomes
- Construct tables before entering data.
- Use correct quantity/unit headings.
- Record raw and calculated data appropriately.
- Maintain consistent decimal places.
- Handle repeats and means clearly.
8.1 Table structure
A results table should be drawn with ruled rows and columns. Each column heading contains the quantity name or symbol followed by a solidus and the unit, for example time / s or potential difference V / V.
Units are not repeated in every body cell. The independent variable normally appears in the first column, followed by raw dependent readings, repeats, means and derived quantities in a logical order.
8.2 Raw readings and derived values
Raw readings are direct instrument observations. Derived values are calculated, such as resistance, density or period. Do not replace raw readings with only the calculated result when the question expects evidence of measurement.
If timing ten oscillations, record the total time and then calculate the period. This allows the method and arithmetic to be checked.
8.3 Decimal places
Raw readings from the same instrument should normally have the same number of decimal places. If a stopwatch reads to 0.1 s, record 8.0 s rather than 8 s when other times are 9.3 s and 10.1 s.
Calculated values are rounded to appropriate significant figures, usually matching the least number of significant figures in the raw data used for that calculation. Do not round intermediate values too early.
8.4 Repeats and anomalies
Place repeat readings in separate columns and calculate a mean. If one repeat is clearly anomalous, investigate and repeat it rather than silently excluding it. Any exclusion should be justified by inconsistency with the other repeats or an observed procedural problem.
Qualitative observations, such as ‘lamp becomes brighter’ or ‘image is sharp and inverted’, should be recorded in clear words rather than forced into numerical columns.
8.5 Ratios and transformed quantities
When a relationship is clarified by a transformed quantity, include that column with its unit: T² / s², 1/L / cm⁻¹ or V/I / Ω. A ratio is written x : y when the question asks for a ratio.
The headings of graph axes can often be copied directly from table headings, reducing unit errors.
Worked examples
Correct heading
For current, use I / A. Do not write I(A), A/I or put A beside every number.
Mean with an anomaly
Times 12.1 s, 12.2 s and 15.8 s suggest 15.8 s is anomalous. Recheck the method and take another reading before calculating a mean.
Practical focus
Investigation or training activity
Design blank tables for a spring experiment, a cooling experiment and a current–voltage experiment. Include repeats and every derived quantity needed for the intended graph.
Examination guidance
- Draw the table before entering values.
- Use quantity / unit headings.
- Keep raw-reading decimal places consistent.
- Show repeat readings, not only the mean.
- Do not place units in table-body cells.
Check your understanding
- Where is the unit written in a table?
- Why record total time as well as period?
- What should be done with an apparent anomaly?
- How should readings from the same instrument be formatted?
Answers
- In the column heading after a solidus.
- It preserves the raw measurement and allows the calculation to be checked.
- Investigate and repeat; exclude only with justification.
- With consistent decimal places.
