Scientific questions and observations

Correct answer: B. Giving different amounts of water and calling water amount the independent variable

The deliberately changed amount of water is the independent variable. In exams choose the factor that is actively changed.

Correct answer: A. Parallax error

Viewing from above can cause an incorrect liquid-level reading. In exams read the meniscus at eye level.

Correct answer: B. To obtain a representative value from repeated measurements of the same length

The average of repeated comparable measurements reduces the effect of random variation. In exams average only comparable values.

Correct answer: B. Time span of the experiment

Without the total duration it is unclear how long observations continued. In exams record both interval and total duration.

Correct answer: C. By the time taken for the foam to disappear

The time taken for foam to disappear is a clear measurable indicator of stability. In exams choose an operational measure for an abstract property.

Correct answer: C. Record values in a table with variables units and time

A table with clear headings units and time makes data comparison easier. In exams choose complete and structured recording.

Correct answer: B. The data may become biased

Omitting unsuccessful trials prevents the data from representing the true results. In exams understand that all trials should be recorded.

Correct answer: B. How does the number of birds observed differ between morning and evening?

The number of birds can be counted at fixed times so the question is testable. In exams choose clear counts for field studies.

Correct answer: B. Select plants of similar initial size or measure change in growth

Similar starting size or measuring change in growth makes the comparison fairer. In exams control initial differences.

Correct answer: B. Different students independently test using the same method

Similar results obtained independently by different people using the same method indicate reproducibility. In exams identify independent verification.

Correct answer: B. Sugar dissolved at a faster rate in hot water

The data supports only that sugar dissolved faster in hot water in this investigation. In exams keep conclusions within the limits of the data.

Correct answer: C. Length is eight point three centimetres

A one-millimetre division supports a reading to one decimal place in centimetres. In exams do not report more decimal places than the instrument allows.

Correct answer: A. Accuracy

Incorrect calibration can shift all readings away from the true temperature. In exams connect calibration with accuracy.

Correct answer: B. How many students in the school read science news daily?

Information about students' habits can be collected through a questionnaire or survey. In exams choose the method according to the question.

Correct answer: B. The sample may not represent the whole area

A roadside sample may not represent conditions across the whole area. In exams identify sampling bias.

Correct answer: B. If light duration increases then weekly plant height increase will rise

This statement gives a testable prediction linking the independent and dependent variables. In exams identify a clear if-then hypothesis.

Correct answer: C. Check the measurement and method then repeat the trial

An unusual value may result from error or real variation so it must be checked. In exams do not remove an outlier without evidence.

Correct answer: B. Complete details of apparatus materials procedure variables and measurements

A complete method and description of variables allow the investigation to be repeated. In exams choose a detailed procedure for reproducibility.

Correct answer: B. Record initial and final height and the time interval

Change in height and time make growth rate measurable. In exams replace vague words with numerical data.

Correct answer: C. A permanent precipitate formed when two solutions were mixed

Formation of a new solid precipitate can be direct evidence of a new substance. In exams identify clear evidence of change.

Correct answer: A. Convert all values to the same unit

Numerical comparison is valid only after conversion to a common unit. In exams standardise units before comparing.

Correct answer: A. It is broader than the sample supports

Applying results from one species to all plants is an unjustified generalisation. In exams keep conclusions within the sample limits.

Correct answer: C. Record the temperature of cooling water every two minutes

Regular short intervals are suitable for a moderate change such as cooling water. In exams choose intervals according to the rate of change.

Correct answer: A. Variability and repetition in the data

Wide spread may reduce confidence in the difference between averages so variability must be examined. In exams do not rely only on the mean.

Correct answer: C. Question hypothesis test data analysis and conclusion

A scientific investigation moves from a question to a hypothesis then testing data analysis and conclusion. In exams remember the logical sequence.