1 — SPECIFIC
Does it name exactly what is being changed and exactly what is being measured? “How does light affect plant growth?” is too vague — which aspect of light? Which aspect of growth?
2 — ONE VARIABLE
Does it change only one thing at a time? Testing sunlight and soil moisture and temperature together means you can never know which factor caused the result.
3 — MEASURABLE
Can the result be expressed as numbers or collected data? If you cannot measure the outcome with a tool or a count, the question needs refining.
4 — EXPERIMENTAL
Can it be answered by running an experiment or making observations? Watch for these traps: “Why…” questions (seek explanations, not results), opinion questions (“best,” “should”), and future predictions (“will ever,” “by the year”).
Grass & sunlight example — spot what is wrong with each:
✗ Too vague: “How does light affect plant growth?” — which type of light? What aspect of growth? Nothing specific is named
✗ Still too vague: “How does shade affect grass growth?” — how is shade measured? What aspect of growth?
✗ Multiple variables: “Do sunlight, soil moisture, and temperature all affect how tall grass grows?” — three things changed at once
✗ Why question: “Why do plants grow more slowly without direct sunlight?” — asks for an explanation, not an experimental result
✓ Testable: “Does the number of hours of direct sunlight per day affect how tall (in cm) a grass plant grows over 3 weeks?” — specific, measurable, one variable, experimental