Hi @Shaz12… to answer your query null hypothesis is the statement that we are actually trying to reject and we are by doing that are trying to prove the alternative…we want to prove that each bottle has an average of 16 ounces… which can be less than or greater than 16 but not equal to 16. Therefore we state Ho as equal to 16 as we want to reject it and accept the alternative Ha which we state as not equal to 16…hope this answers your question.
You don’t (really) ever have “proof” of the null hypothesis (especially) or of the alternative hypothesis, irrespective of what the data show (you can have data that support the alternative, but it isn’t proof).