Recording and analysing data

Correct answer: D. Repeat observations and record them promptly

Repeating an observation reduces the effect of chance errors or unusual results. Recording it promptly also prevents details from being forgotten or altered, so option D is the most reliable method. Observing only once gives limited evidence, and recording preferred or expected results introduces bias. Exam tip: For reliability, look for ideas such as repetition and prompt recording.

Correct answer: B. Record numerical values using a standardized thermometer

For a precise comparison, the student should record numerical temperature values with a standardized thermometer, so option B is correct. Words such as hot, cold and normal are subjective categories: two people may use the same word for different temperatures. A numerical reading, such as a value in degrees Celsius, gives a fixed and comparable record. Using the same properly calibrated instrument and the same unit also makes observations more reliable and repeatable.

Changing category colours does not make the observations more exact, because the underlying descriptions remain vague. Keeping only the hot category removes useful information rather than improving it. Writing values from memory can introduce errors and does not provide a dependable measurement. A standardized thermometer directly measures temperature and records a number that can be compared across times, places or students. Therefore option B is the scientifically appropriate improvement.