What is a null hypothesis?

Hi Elliot, a null hypothesis is what we believe to already be true, we then do an experiment to try to see if the null hypothesis is not true. For example, if I want to do an experiment to see if a dice is fair (that is to say, there is an equal probability of landing on each side), my null hypothesis would be "this dice is fair", I could then start rolling the dice to test my null hypothesis. Lets say I rolled the number 2 twice in a row, I might be suspicious that my nice isn't fair, but probably not enough to reject my null hypothesis. Now what if I rolled the number 2, three, four, five, six, times in a row? At some point I would reject my null hypothesis, but that is for me to decide, and I must do so before I conduct the experiment.

Hello Elliot, A null hypothesis means that there is no difference or relationship between things we are studying. It's like saying "nothing interesting is happening." Its purpose is to be the starting point for testing whether something is actually happening or not. Let's imagine we have two groups of kids, Group A and Group B. We want to see if there is a difference in their average height. The null hypothesis would be that the average height of Group A is the same as the average height of Group B. To test this, we measure the heights of the kids in both groups. We calculate the average height for each group and compare them. If the averages are very close, it supports the null hypothesis. But if they are very different, it suggests that something interesting might be happening. So, the null hypothesis helps us decide if there is enough evidence to say that something is really happening or if it's just due to random chance. It's like a starting point that we want to challenge with our data.

A null hypothesis is the initial assumption made before an experiment. It is often used to prove or disprove an assumption made in a question which you will see in an exam.