Scientific Enquiry, Observation, Measurement and Recording
This domain tests how to plan a fair test, choose the right instrument and unit, record results clearly and draw a conclusion that matches the data.
Planning a fair test
A fair test changes one independent variable, measures one dependent variable, and keeps every other variable the same. These are the control variables. Write a hypothesis as a testable statement, for example 'plants given more light grow taller'. Repeat readings and calculate a mean to reduce the effect of random errors. Precision means readings are close together; accuracy means they are close to the true value.
Measuring and recording
Choose a suitable instrument and unit: ruler (mm or cm), measuring cylinder (cm³, read at eye level at the bottom of the meniscus), thermometer (°C), balance (g), stopwatch (s) and newton meter (N). Put units in the column headings of a results table. Use a bar chart for categories and a line graph for continuous data such as temperature over time. A conclusion should quote the data and answer the question; an evaluation should describe errors and suggest improvements.
Worked example
Test whether more light makes cress grow taller. Change the distance of the lamp (independent variable), measure shoot height in mm after ten days (dependent variable), and keep the same water volume, soil type, pot size, number of seeds and room temperature. Measure each pot the same way and repeat the whole test.
Traps that cost marks
Changing two variables at once makes the test unfair. Saying one trial 'proves' a hypothesis is too strong; say the data supports it. Do not use a line graph for categories, and never leave units off headings.