Junior School: Planning a Fair Scientific Test

Planning a fair scientific test

A fair test compares the effect of one chosen change while keeping other relevant conditions comparable. In this junior-school activity, you will turn a vague claim about paper into a testable question, identify variables, examine repeated readings and write a conclusion that fits the evidence. Everything needed is supplied below. The records are invented teaching data; nobody is claiming that these results came from an experiment.

From a claim to a measurable question

“Paper B is best” is too vague. Best for drawing, wrapping or soaking up water? Our question is narrower: How does paper type affect the height of the wet front after 60 seconds in this model? The wet front means the highest visible boundary reached by water above a marked starting level. We measure that height in millimetres. It is a distance measurement, not a direct measurement of the total volume absorbed.

Complete this as a paper-and-data task. You do not need water, glassware or a practical setup. If a teacher separately demonstrates paper wicking, the teacher must choose suitable equipment, supervise it and manage spills away from electrical equipment. That demonstration would produce its own observations; it would not turn the fictional numbers here into real measurements.

Completed planning sheet

A controlled condition is something kept comparable. It is not the same as a separate control treatment. This question compares three paper types; it does not need a fourth treatment called “the control” merely to use scientific vocabulary. “Keep everything the same” is also incomplete, because paper type deliberately changes.

Optional teacher-supervised classroom plan

A teacher may use plain paper strips, a ruler, pencil, timer and a stable shallow plastic tray of clean water. Use no chemical additives, heating or electrical equipment near the tray. The teacher chooses the materials and location, prepares any cut strips, checks that wet edges can be seen and manages spills. Nothing is tasted. This plan is optional; the supplied-data task remains complete without it.

1. Prepare three fresh 20 mm × 100 mm strips of each paper type. Mark a pencil baseline 10 mm above each lower end.
2. Identify each strip by type and repeat number. Record the question and the controlled conditions before collecting data.
3. Use the same tray arrangement and water temperature. Keep the baseline at the water surface, with the lower 10 mm immersed; support the strip upright in the same way without touching the tray sides.
4. Start timing when the strip first contacts the water. At 60 s, read the vertical wet-front height above the baseline using the same rule each time.
5. Record the actual value and unit immediately. If the wet front is unclear or uneven, note that rather than inventing a precise result.
6. Repeat with a fresh dry strip, restoring the stated starting conditions. Collect three readings for every type and calculate means only from valid recorded values.
7. Keep these classroom observations separate from the simulated table below. Discuss differences without adjusting actual readings to match the example.

Read the repeated observations

For A, mean = (22 + 24 + 23) ÷ 3 = 69 ÷ 3 = 23 mm. Its range is highest minus lowest: 24 − 22 = 2 mm. For B, the total is 105 mm and the mean is 35 mm. For C, the total is 84 mm and the mean is 28 mm. The mean difference between B and A is 35 − 23 = 12 mm.

These repeated values show variation, even within one paper type. Repeats help reveal such variation; they do not repair a biased ruler or an unfair design. Three consistent readings are useful evidence for this supplied comparison, but they do not prove that every brand or batch will behave the same way.

Compare a fairer design with an unfair one

In Design 1, A and B use equal-sized strips, the same water conditions and the same 60-second interval. Paper type is the intended change. In Design 2, A uses a 20 mm-wide strip for 30 seconds, while B uses a 40 mm-wide strip for 60 seconds. Type, width and duration change together. Even if B reaches a greater height, Design 2 cannot isolate the effect of paper type.

A useful repair names the changes: use equal-width and equal-length strips, the same starting conditions and the same reading time, then repeat with fresh strips. Repeating Design 2 ten times would still leave its differences entangled. Do not “correct” its readings by dividing by two: the record supplies no rule that doubling time or width doubles wet-front height.

Write a limited conclusion

Worked response: “In the simulated 60-second comparison, B had the greatest mean wet-front height, 35 mm, compared with 28 mm for C and 23 mm for A. The readings support greater upward wicking by B under the stated conditions. They do not establish which paper absorbs the greatest total volume or works best for every purpose.”

The numerical comparison is an observation about the supplied record. The explanation linking the pattern to the paper is an interpretation, supported only while the stated controls hold. Avoid changing “supports” into “proves forever”. Also avoid claiming a cause such as a particular pore size, because no pore measurements were supplied.

Independent practice: repair and interpret

1. A learner changes paper type and water temperature together. Name the independent variable intended by our question and the unwanted difference.
2. A new fairer comparison supplies X: 18, 20, 22 mm and Y: 25, 26, 27 mm, all after 60 s. Find both means and ranges.
3. Write one evidence-based conclusion and one limit for X and Y.
4. The third reading for another strip is missing. Explain why writing 0 mm would be wrong.

Answers and learning rubric: 10 marks

1. Paper type is intended to change; water temperature is the confounding difference. Keep temperature comparable. Award 1 mark for each variable identified: 2 marks.
2. X mean = 60 ÷ 3 = 20 mm; range = 22 − 18 = 4 mm. Y mean = 78 ÷ 3 = 26 mm; range = 27 − 25 = 2 mm. Award 1 mark for each correct value with unit: 4 marks.
3. Y has the higher mean by 6 mm in this simulated 60-second comparison: 1 mark. Accept a relevant limit, such as no direct total-volume measurement or no evidence about other conditions: 1 mark.
4. A missing reading is unknown, whereas zero would assert that a valid reading found no rise: 1 mark. Leave it clearly marked missing and do not invent it: 1 mark.

Review the reason for each lost mark. If variable identification was difficult, rewrite the question using “change” and “measure”. If the calculation was difficult, keep the individual values beside the mean. If the conclusion was too broad, add the actual conditions and remove the unsupported claim. This is an original learning rubric, not an official examination scheme.

Background: Science Buddies: experimental variables. The worked paper-wicking activity and data here are original.

More junior-school revision

For broader navigation, use the junior-school resource collection or the Grade 9 topical resource index. Check individual access conditions and contents; this lesson does not verify a particular member file or an exact current grade/term allocation.