This week I learnt that I have been confusing people for years about what a hypothesis really is. A conversation with Erin and Craig helped me understand my mistake (tl;dr I oversimplified, a lot) and this post by Erin does a great job of explaining the confusion and why it matters.

The relationship between hypothesis and prediction is many-to-many. A single hypothesis (i.e. proposed explanation for a phenomenon) might result in many different predictions (i.e. expected observable outcomes if the hypothesis is true); and a single prediction might be explained by many different hypotheses.

  • Hypothesis 1: light helps plants grow.
  • Hypothesis 2: heat helps plants grow.

  • Prediction 1: if I put my plants in the warm sun, they will grow more.
  • Prediction 2: if I put my plants in the cold cellar, they will grow less.

Both these hypotheses are consistent with both these predictions. If I put my plants in in the sun and they thrive, I will not know if this was because of the light or because of the heat. To disentangle these two, I need a prediction which is consistent with one of the hypotheses but not the other.

  • Prediction 3: if I put my plants in a cold place under the sun, they will grow more.
  • Prediction 4: if I put my plants in a warm dark place, they will grow more.

These two predictions are only consistent with one of the hypotheses. If we can test and reject one of them, we can pinpoint which hypothesis has been falsified.1

By teaching people to include a prediction in the their hypothesis, I may have been stunting their ability to effectively reason through these sorts of situations. By simplifying one thing too much, I have made other things more complicated.

If you are one of the many, many people potentially affected by my mistake, then I apologise for the confusion. I will try to do better next time.

Teachers are also forever learning. Please give us feedback so that we may improve. Thank you Erin and Craig for helping me grow. ❤️

  1. Plants probably need both heat and light, because life is never as simple as the contrived examples we use to explain things.