I know how to get a critical value but I am not sure now how to do it when they added "when testing the claim that p = 1/2"....
how did they get the answer for critical value ?
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I have the impression that it is $\alpha =1$% . If so, you need to find how how many $z$'s , you need to go in either direction of the mean to cover $99$% of the distribution: http://www.mathsisfun.com/data/standard-normal-distribution-table.html – user99680 Dec 01 '13 at 00:13
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that is right!...I was looking at the wrong table :( – manual Dec 01 '13 at 00:18
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why is it not letting me vote up for you ughhh – manual Dec 01 '13 at 00:18
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I wrote a fuller answer below. – user99680 Dec 01 '13 at 00:20
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The critical values are the set of $z-$ values {$z_0,-z_0$} that have the property that $\alpha$% of the probability lies in the interval $(z_0, -z_0)$. As an example, if you know the $1-2-3$ rule, a.k.a $68-95-99.7$% rule, you know that the critical values for $\alpha=68$ are {$-1,1$} , the critical values for $\alpha=95$% are {$-2,2$}, etc. You can look up in this table: http://www.mathsisfun.com/data/standard-normal-distribution-table.html , how to get critical values for a given significance level: since you're doing a 2-sided test, just move the cursor to the place where you read the percentile $(1-\alpha)/2$.
user99680
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I need someone to vote up, I dont have 15 reps so I can accept the asnwer..thank for taking the time....now I understand it . – manual Dec 01 '13 at 00:28
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It would be good if we could see the entire question, but if it is the Sign-Test, then it make sense to use p = 1/2 because it is either "yes" (assigned a plus) or a "no" (assigned a minus, hence the name of the test) But again, more information about the question would be useful
imranfat
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that tells me what the minus and plus sign..but how did they get 2.575 ?? because significance level of 0.01 would be 2.33 so why is it 2.575 ? – manual Dec 01 '13 at 00:07