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# S2 - quick hypothesis test watch

1. Can't seem to get my head around this two tailed stuff, would appreciate some help on this question I have no clue what so ever so would be grateful for some clear, easy explinations. Thanks

Q: Using binomial distribution:

Ho: p=0.5 H1: p =/ 0.5 (two tailed test)

n=20, x=7, using 10% level of significance.

(I know how to do it if the H1 is a 'p < ' or 'p > ' statement but not when it's the 'p =' sign i.e a two tailed test)

EDIT: Okay I've got the answer somehow by fiddling around with things, but I don't understand how and why I do it.
Using X~B(20, 0.5) I did P(X<7) = 0.1316 and multiplied this probability by 2 to get 0.2632 which is the final answer but I suspect this is not the right method?
2. (Original post by Playboy King)
but I suspect this is not the right method?
it is - binomial distributions are symmetrical, so just multiply the answer by 2
3. (Original post by Pheylan)
it is - binomial distributions are symmetrical, so just multiply the answer by 2
Oh I see, that makes sense
Quick question, why do we use (P < 7) instead of (P > 7)?

With the one tailed tests I use whatever the sign is on H1 but with this it's =/ so how do we know which one to use?

(by < I mean equal to or smaller than, I just can't put the symbol with the extra line underneath in lol)
4. (Original post by Playboy King)
Oh I see, that makes sense
Quick question, why do we use (P < 7) instead of (P > 7)?

With the one tailed tests I use whatever the sign is on H1 but with this it's =/ so how do we know which one to use?

(by < I mean equal to or smaller than, I just can't put the symbol with the extra line underneath in lol)
i'm not sure, but i just use < and then x2, seems to work so i don't question it

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