Scientific Method in MYP Science: Predictions, Hypotheses & Variables (with the Butterfly Effect)
Every science investigation, from a Year 7 experiment to real research, rests on the same handful of habits: asking a testable question, predicting what will happen, and controlling what could confuse the result. Those habits are what Criterion B (Inquiring and designing) assesses — and they are easier to learn by trying them than by reading about them.
Try it yourself: predict outcomes, write hypotheses, sort real scenarios into field and lab investigations, and earn badges along the way, with a theme built around the butterfly effect. Progress saves on this device.
Prediction vs hypothesis
A prediction states what you expect to happen: "the plant near the window will grow taller". A hypothesis goes further and gives a testable explanation: "plants grow taller with more light because light drives photosynthesis". The "because" is what turns a guess into something you can test and explain. In Criterion B the explanation is what earns the higher bands.
The three kinds of variable
A fair test changes one thing and keeps everything else the same:
- •Independent variable — the one thing you deliberately change (amount of light).
- •Dependent variable — the thing you measure as the result (height of the plant).
- •Controlled variables — everything you keep the same so the test is fair (water, soil, pot size, temperature).
Field investigations and lab investigations
A lab investigation lets you control almost everything but is artificial. A field investigation happens in the real environment, which is more realistic but harder to control — weather, time of day and other organisms all interfere. Good scientists can say which approach suits a question and name the trade-off.
Why the butterfly effect belongs in a science lesson
The "butterfly effect" comes from the study of chaotic systems such as the weather, where a tiny difference at the start can grow into a very different outcome later. It is a reminder of why scientists control variables and record their methods precisely: small uncontrolled differences can change the result, and if you did not write them down you cannot explain what happened.
Writing a method others can repeat
A strong method lists the materials, states exactly what is changed, measured and kept constant, and gives steps clear enough for someone else to repeat. If a stranger could not run your experiment from your write-up, the method is not finished.
Frequently asked questions
A prediction says what you expect to happen. A hypothesis also gives a testable scientific reason (often using "because") for why it should happen.
The independent variable is what you change, the dependent variable is what you measure, and controlled variables are the factors you keep the same to make the test fair.
Criterion B, Inquiring and designing, covers formulating a hypothesis, identifying variables and designing a method. Criterion C covers processing and evaluating the results.