I'm trying to understand the correct ways of expressing a null hypothesis. So I've created this case and I'd like to know if I'm on the right track.
Case 1: There is a general understanding that keeping a pot closed with a lid reduces the time taken to cook. This is because more heat is trapped in the pot. I (as a researcher) seem to have a different view that other factors such as the type of pot also matters. So I want to test if this is true and I'm going to test a number of different types of pots both with and without the lids on.
Null Hypothesis (I hope I'm correct here) : There is no difference is cooking time, whether or not the pot is covered
My question in this regard: I'm confused about the null hypothesis being the 'default' situation with 'no change'. So I also tend to think that the null hypothesis is the generally accepted condition that cooking with the lid on reduces cooking time.
So what is my correct null hypothesis?