Say you have a friend who asserts that they can smell water. You are sceptical, yet also curious. To test their claim, you fill up 50 cups out of 100 with water and instruct your blindfolded friend to sniff away.
If your scepticism – the null hypothesis – is justified, the odds of your friend identifying all 50 filled cups are very slim. In fact, they will get it right only about half the time, through simple luck. This would be the “null result” of the test.
Any careful investigation proceeds in this spirit, with a null hypothesis determined by the context. In court, you are innocent until proven guilty. In experiments of fundamental physics, you will often hear that today’s discovery is tomorrow’s null hypothesis.
