Scientific questions and observations

Correct answer: C. Repeat measurements calculate the average and check instrument precision

Repeated measurements and averaging reduce the effect of random error. Instrument precision should also be checked.

Correct answer: C. The leaf colour has changed from green to yellow

The direct answer is C: the leaf colour has changed from green to yellow. An observation states only what can be directly seen or measured, without claiming the cause. A visible colour change can be recorded by looking at the leaves, so option C is the observation. Option A, saying that the plant lacks minerals, is an inference about a possible cause; mineral deficiency might be one explanation, but it needs testing. Option B, saying that the plant is diseased, is also an interpretation and cannot be proved merely by seeing yellow leaves. Option C is correct because it reports the visible change without adding an explanation. Option D, saying that the roots have stopped absorbing water, proposes another hidden cause that would need evidence, such as measurements or a controlled investigation. In science, first record the fact, then suggest possible explanations, and finally test those explanations. Memory cue: “what I see” is observation; “why it happened” is inference or hypothesis.

Correct answer: B. Testability

An opinion-based question is difficult to test with evidence so it lacks testability. In exams look for measurability.

Correct answer: B. Measure dissolved air level and temperature at different times

Taking related measurements over time helps examine patterns and possible causes. Systematic data are more reliable.

Correct answer: B. Qualitative and quantitative

Colour describes a quality while mass is measured with a number and unit. Understand the difference between qualitative and quantitative observations.

Correct answer: C. Does changing daily hours of light alter plant height in seven days?

The direct answer is C: changing the daily hours of light and measuring plant height after seven days is the most precise question. A strong scientific question identifies what will be changed, what will be measured and often the time period. Here, hours of light are the independent variable, plant height is the dependent variable, and seven days gives a clear observation period. Option C is correct because another investigator could understand and test it. Option A, “Are plants good?”, is vague because “good” has no defined measurement. Option B, “Why do plants grow?”, is very broad and may involve many factors, so it does not state a manageable test. Option D, “Is nature wonderful?”, is a personal or philosophical question and has no clear measurable variables. A precise question should avoid vague words and define the comparison. The wording does not guarantee a particular result; it only makes the investigation testable. Exam cue: look for variable, measured outcome and time limit.

Correct answer: B. The sampling time is not representative

One day's data do not represent seasonal and daily variations. Observe at multiple times to obtain a representative sample.

Correct answer: B. Use a standardized odour assessment or multiple independent observers under safe conditions

Odour descriptions can be subjective so standardization or multiple observers improve reliability. Safety rules are essential.

Correct answer: B. The recorded precision exceeds the instrument's capability

A measurement should be reported only to the precision allowed by the instrument. Avoid false precision.

Correct answer: B. Count the number of bubbles in a fixed time

Counting bubbles in a fixed time makes the observation quantitative and comparable. Keep the measurement duration constant.

Correct answer: B. Confirmation bias

The student is selecting only evidence that supports a prior belief. Record all results using the same rule.

Correct answer: C. Inference based on observation

Conductivity was not directly tested so it is an inference drawn from shininess. Verify an inference through an experiment.

Correct answer: B. Do different soil types change seedling height in fourteen days?

Soil type is the changed variable and seedling height is the measured outcome. Clear variables make a question testable.

Correct answer: B. Use predefined criteria and a common recording table

When different observers describe the same event in different words, their observations cannot be compared fairly unless the information is recorded in a common way. Predetermined criteria tell everyone what features to look for, while a shared recording table gives the same headings, units, and type of entry. This reduces differences caused only by wording or personal judgement. Therefore option B is the scientifically appropriate choice.

The procedure should be decided before observation begins, so that one observer is not allowed to change the rules after seeing the result. Stopping observation gives no comparable evidence. Keeping only the senior observer's account replaces standardisation with authority and may discard useful data. Mixing descriptions without a common structure can make the information more confusing. A common table does not remove every possible error, but it makes the records clearer and more consistent.

Correct answer: B. Uncontrolled variation related to time of day may affect results

Moisture or other conditions may vary at different times and affect comparison. Keep observation time constant.

Correct answer: A. Occurring afterward does not prove causation

Sequence in time alone does not prove causation because other factors may act. Controlled evidence is needed to establish a cause.

Correct answer: C. Check the measurement procedure and repeat the observation

An unusual value may result from error or a real event so checking and repeating are necessary. Do not remove data without justification.

Correct answer: B. Replace it with measured height or biomass

The direct answer is B: replace “better” with a measured height or biomass outcome. The word “better” is vague because different people may understand it differently: taller, heavier, healthier-looking, or producing more leaves. Science needs an operational definition, meaning a clear statement of exactly what will be measured and how. Option A is wrong because removing the word without naming an outcome leaves the question incomplete and untestable. Option B is correct because plant height can be measured with a ruler and biomass can be measured as mass, using a stated procedure and time period. Option C is wrong because “beautiful” is even more subjective and cannot give a consistent scientific measurement. Option D is wrong because “much better” is still vague and adds no measurement. A strong investigation could compare average height after a fixed number of days while keeping plant type, soil, light, and container conditions controlled. Memory cue: replace opinion words with a number, unit, time, and method whenever possible.

Correct answer: B. Is exposure to different pollution levels related to cough frequency when other major factors are recorded?

A suitable question considers both measurable variables and other influencing factors. Even with an association causal claims require caution.

Correct answer: B. Understand the context and help reproduce the observation

Contextual information helps interpret and reproduce results. Always record conditions during field observations.

Correct answer: B. Lighting conditions affected the colour observation

The light source can affect perceived colour so comparisons should be made under the same lighting. Control observation conditions.

Correct answer: A. The sampling location is biased

Conditions near a road may differ from those inside the forest so the sample is not representative. Sample from different locations.

Correct answer: A. Procedural observation error

Starting the timer late is a procedural error that can distort the measured time. Define the starting point in advance.

Correct answer: B. Instruments procedure time conditions and raw data

A detailed method and raw data allow others to repeat the same procedure. A conclusion alone is insufficient.

Correct answer: B. Convert values to the same unit

Numerical comparison can be misleading without common units. Standardize units before analysing data.