A hypothesis is a claim that an investigation can test. A measurement plan is the set of decisions about what you change, what you measure, how, and what you keep the same. In Co-ordinated Sciences 0654 you are asked to handle both in biology, chemistry and physics contexts, so the skill has to work across all three.
This lesson opens cross-topic experimental evaluation. Everything later in the module depends on keeping the two ideas apart.
Why keep the idea and the method apart?
The hypothesis says what you think is true. The plan says how you will find out. If the two are mixed, a reader cannot tell whether a weak result means the idea is wrong or the method was poor.
Try a quick test: can data check the sentence? If it contains words like “will measure”, “using a balance” or “five times”, it belongs to the plan. If it says how one quantity affects another, it is the hypothesis.
Building the pair step by step
- State the claim with both quantities named: “As X increases, Y increases (or decreases)”.
- Name the independent variable (the one you change) and give its range and unit.
- Name the dependent variable (the one you measure), the instrument, its unit and the resolution.
- List the control variables that must stay the same.
- Say how many repeats and what you will do with them, such as calculate a mean.
Worked example
All numbers in this lesson are invented for teaching.
Scenario: A student suspects that sugar dissolves faster in warmer water.
Hypothesis: The higher the water temperature, the shorter the time for sugar to dissolve.
Measurement plan:
| Part | Decision |
|---|---|
| Independent variable | Water temperature: 20, 30, 40, 50 °C, read with a thermometer to 1 °C |
| Dependent variable | Time until no crystals are visible, in seconds, from a stopwatch reading to 0.1 s |
| Control variables | Water volume 100 cm³, sugar mass 5.0 g, same stirring rate, same beaker type |
| Repeats | Three runs at each temperature, then calculate the mean time |
Check the logic: 4 temperatures × 3 runs = 12 runs in total. The hypothesis names two quantities and a direction. The plan says how each is measured, in which unit, and what stays fixed.
The invented prediction would be that the mean time at 50 °C is shorter than at 20 °C. If the data showed the reverse, the hypothesis would not be supported, and the plan would still be a fair test.
The mistake to watch for
A common answer to “state a hypothesis” is a plan in disguise.
Mistaken answer: “I will measure the time for sugar to dissolve at four temperatures using a stopwatch.”
This describes an action. It does not claim anything that data could contradict. The correction is to add the relationship: “The higher the temperature, the shorter the dissolving time.” Then put the stopwatch and temperatures into the plan.
The reverse slip also appears: writing a hypothesis such as “the experiment will be accurate” is a comment about method, not a claim about the science.
Check yourself
1. Is this a hypothesis or part of a plan? “Plants given more light will have a greater mass after two weeks.”
Show answer
It is a hypothesis. It links two quantities (light and plant mass) and could be contradicted by data.
2. A student writes: “Keep the volume at 50 cm³ and use a measuring cylinder.” Which part of the plan is this?
Show answer
It is a control variable decision with an instrument. It belongs in the plan, not in the hypothesis.
3. Write a hypothesis, then name the independent and dependent variables, for this question: does a heavier trolley roll further after leaving a ramp?
Show answer
Hypothesis: the greater the trolley mass, the further it rolls after the ramp. Independent variable: trolley mass (kg). Dependent variable: distance rolled (m). Ramp height and surface should be controlled.
Where this leads next
Once you can write the pair cleanly, move to identifying confounding variables in a mixed scenario, which tests whether your plan really isolates one change. The scientific investigation critic gives a structured way to practise on your own descriptions.
Some students find the plan is the harder half to write precisely. Our teachers work through that gap in online one-to-one Co-ordinated Sciences tuition.