# Chi squared undersanding doubtWatch

#1
Hey guys I have two doubts, for chi squared test what is the difference between the meanings 'difference due to chance' and 'significantly difference'
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1 week ago
#2
Hi, Stormragexox (try to keep tabs over your explosive temper, yeah? !

Let me try and explain this in simple terms. IN any statistical test where you work out a parameter, and then look up its p value in a table (or calculate it e.g. in a paired t test):-

a) the null hypothesis normally states the opposite of what you are trying to prove.
b) so your aim, in order to prove your intended idea, is to prove that the null hypothesis is v unlikely to be true.

SORRY, BEAR WITH ME - I KNOW YOUR Q is different - coming to that in a sec!

c) If you have set your significance level at p < 0.05 (the usual scenario), then this means that THE NULL HYPOTHESIS has a 5% [0.05 as a percentage] probability of being false due to chance [e.g. two sets of results being different due to chance where the null hypothesis states that they are NOT different] i.e. it has a 95% chance of ACTUALLY being false i.e. as mentioned above, you have almost certainly proved it untrue i.e. your results are significant (significantly different if that is what you set out to prove e.g. if you are trying to show that a drug "works", then you might be trying to show that patients given the real drug have a significantly different effect from those given placebo (dummy medicine)).

It is a concept that is a bit difficult to grasp, but if you look at some examples, it will become easier to understand.

If still stuck, let me know and I shall explain in a different way.

M.
Last edited by macpatgh-Sheldon; 1 week ago
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