Investigable vs Non-Investigable Questions
A wellness video claims celery juice cures anxiety. Before you believe it or reject it, ask a sharper question, can this even be tested with a fair investigation?
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A friend asks three questions: "Does playing music to plants make them grow faster?", "Is rock music better than pop?", and "Which is the best colour?"
Which of these could you actually answer with a scientific investigation, and which could you not? What makes the difference?
An investigable question is one you can answer by collecting data through a fair, repeatable investigation. Three features make a question investigable. First, it names a variable you can change (the independent variable) and a variable you can measure (the dependent variable). Second, it is specific and focused, not vague. Third, it can be answered with the resources you actually have: the time, equipment, samples and safety limits of a real classroom or lab.
Compare two questions about plants. "Is sunlight good for plants?" is not investigable, "good" is not something you can measure, and the question is too broad. But "Does the daily hours of light (4, 8 or 12 hours) affect the height of radish seedlings after 14 days?" is investigable, because you can control the light, measure the height in centimetres, and finish within a fortnight.
"Does the brand of battery affect how long a toy car runs?" is investigable. You can swap the battery brand (the variable you change), time how long the car runs in seconds (the variable you measure), keep the car and surface the same, and repeat the test. Every part can be measured or controlled.
When the CSIRO studies whether a new wheat variety yields more grain, researchers do not ask "is this wheat better?" They ask a sharp, investigable question: "Does variety X produce more tonnes per hectare than variety Y under the same rainfall and soil?" Only that version can be tested with data.
A question can sound scientific and still not be investigable. "Why is the universe so amazing?" uses science words but has no measurable variable. Investigability is about whether you can collect data to answer it, not about whether it sounds clever.
Know
- An investigable question can be answered by collecting data through a fair test.
- Variables are things you can change, measure or keep the same.
Understand
- Why questions of opinion, value or impossible scale cannot be investigated.
- How the resources you have shape which questions you can answer.
Can Do
- Sort questions into investigable and non-investigable.
- Rewrite a vague question so it becomes investigable.
Wrong: Any question with a question mark is a scientific question.
Right: A scientific question must point to data you can collect to answer it.
Wrong: If a question is about science, it must be investigable.
Right: "Should we colonise Mars?" is about science but is a question of values, not data.
Wrong: A vague question can be answered if you just try harder.
Right: A vague question must first be rewritten with a clear variable before it can be tested.
Wrong: Resources do not matter when judging a question.
Right: "Does gravity differ on Jupiter?" is testable in theory but not investigable in a school lab, resources decide.
A student lists three "investigable" questions for a project. One is not actually investigable, click it.
- Does the amount of salt added change the boiling time of 200 mL of water?
- Which sport is the most fun to watch on a weekend?
- Does the drop height affect how high a tennis ball bounces?
Some questions are non-investigable, science cannot answer them with data, no matter how good your equipment is. They usually fall into a few groups. Opinion and value questions ("Is jazz better than hip-hop?", "Should phones be banned in schools?") ask what people prefer or what is right, not what can be measured. Untestable questions ask about things outside what we can observe or measure. And some questions are investigable in principle but need resources beyond reach, such as decades of time, equipment a school does not have, or methods that would be unsafe or unethical.
This does not make these questions silly or unimportant. Deciding whether phones should be banned is a real and serious debate. It just is not a question that data alone can settle, which is exactly why we keep it separate from investigable science.
"Is it wrong to test cosmetics on animals?" is an ethical question, not an investigable one. However, "Does ingredient X cause skin irritation in a patch test?" is investigable. Science can supply data about effects, but the decision about what is right also involves values.
Australia's CSIRO can measure how much carbon a forest stores, an investigable question with clear data. Whether we should clear that forest for farmland is a value question that data informs but cannot decide on its own. Good scientists are careful about which kind of question they are answering.
Do not assume a non-investigable question is a bad question. Questions about ethics, value and meaning are important, they simply belong to philosophy, law or personal choice rather than to a fair test with data.
Most real questions start out too vague. The skill is to refine them until they have a clear variable to change, a clear variable to measure, and a scale that fits your resources. Take "Does music help you study?" To make it investigable, decide what to change (type of sound: silence, instrumental music, or song lyrics), what to measure (number of words recalled from a list after 10 minutes), and what to keep the same (the list, the room, the time allowed).
The refined version becomes: "Does the type of background sound (silence, instrumental, lyrics) affect the number of words a student recalls from a 20-word list?" Now it is specific, has measurable variables, and could be done in a single lesson with people who agree to take part. Refining is not changing the topic, it is sharpening the question until data can answer it.
"Are energy drinks bad?" becomes investigable as "Does drinking 250 mL of an energy drink change a person's resting heart rate measured 30 minutes later, compared with water?" The vague word "bad" is replaced by a measurable variable (heart rate) and a clear comparison.
Medical researchers at institutions such as the George Institute in Sydney spend weeks refining one clear question before a trial begins, for example, exactly which dose, measured over exactly how long, compared against exactly what. A sloppy question wastes years of work.
When you refine a question, do not quietly change what you are really asking. Sharpening "does music help studying?" into "does sound type affect word recall?" is fair. Switching it to "do students like music?" answers a different question entirely.
Even a perfectly worded question is only investigable if you can actually do it. Feasibility means checking your available resources: Do you have the time (a 14-day plant study fits a term, a 14-year one does not)? The equipment (a stopwatch and ruler, yes; an electron microscope, no)? Enough samples or participants to see a pattern? And is it safe and ethical, would anyone be harmed, and have people agreed to take part?
A question that fails any of these is non-investigable for you, even if a well-funded lab could answer it. Recognising this early saves you from planning an experiment you can never finish. Scientists call this "scoping", matching the question to the resources before committing to the work.
"Does a year of weekly fertiliser change tree trunk thickness?" is well worded but not feasible for a 10-week project, the time alone rules it out. Swapping trees for fast-growing radish seedlings and a 2-week window keeps the same idea but makes it investigable.
Students often pick questions that need far more time, money or participants than they have, then run out of time. Always ask "can I really finish this safely with what I have?" before you start.
A student wants to test "Does the type of soil affect how tall a gum tree grows?" using real gum trees over the school year. List the single biggest reason this is not feasible for a 10-week project.
How close was your prediction?
Nice, you spotted that resources, not wording, were the problem.
Good to notice, feasibility is about resources like time, not just how the question is phrased.
Speed Round · 6 questions
True or false? Tap as fast as you can. Build a streak.
An investigable question must have a variable you can measure.
"Which song is the best?" is an investigable question.
A question can be testable in theory but non-investigable for you because of limited resources.
Refining a question means changing the topic to something easier.
The independent variable is the one you deliberately change.
Ethics and safety have nothing to do with whether a question is investigable.
How are you completing this lesson?
Think back to the three questions from the start: music and plant growth, rock vs pop, and the best colour.
Which one is investigable, and how would you rewrite one of the others so science could test it?
Quick Check · 5 questions
Check Your Understanding · 3 questions
1. Write one investigable question and one non-investigable question about sport, and explain what makes each one what it is.
2. Why might a well-worded question still be non-investigable for a Year 9 class? Give one reason linked to resources.
3. Rewrite "Does sleep help learning?" so it becomes an investigable question, naming the variable you would change and the one you would measure.
Show Your Working · 3 questions
SA1. Describe two features that make a question investigable, and give an example question that has both features.
SA2. Explain why questions about ethics or value, such as "should we test medicines on animals?", are non-investigable, even though they involve science.
Hint: Think about what data can and cannot decide.
SA3. A student proposes: "Does music make plants grow taller?" Evaluate whether this is investigable, then rewrite it as a fully investigable question, naming the variables and checking it is feasible.
Quick Check
1. C. It names a variable to change (fertiliser) and one to measure (height) and is specific.
2. B. "Should governments ban single-use plastic?" is a value question, not one data can decide.
3. C. The amount of light is the factor deliberately changed, so it is the independent variable.
4. B. Feasibility is about whether the investigation can be done with your time, equipment and ethics.
5. C. Measuring grams of sugar in named drinks replaces the vague word "unhealthy" with data.
Show Your Working Model Answers
SA1 (4 marks): An investigable question has a variable you can change [1] and a variable you can measure [1]. It is also specific rather than vague [1]. Example: "Does the drop height (10, 20, 30 cm) affect how high a tennis ball bounces?" [1].
SA2 (4 marks): Ethical questions ask what is right or what we should do [1]. There is no variable you can measure to settle right and wrong [1]. Data can tell us the effects of a choice, such as how an animal responds [1], but the decision also depends on values, so data alone cannot answer it [1].
SA3 (5 marks): As written it is borderline, "music" and "grow taller" need defining [1]. Rewrite: "Does playing 4 hours of music per day (vs silence) change the height of bean seedlings after 14 days?" [1]. Independent variable: music vs silence [1]. Dependent variable: seedling height in cm [1]. It is feasible because seedlings grow fast and the test fits a fortnight with simple equipment [1].
Investigable
Answerable with data from a fair test
Variable
A factor you change, measure or control
Independent
The factor you deliberately change
Dependent
The factor you measure
Non-investigable
Opinion, value or impossible scale
Feasibility
Can you do it with your resources?
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