p-value and alpha value, Need help from the statistics experts
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 Dec 7 2013, 12:44 PM
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#1
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3,713 posts Joined: Nov 2011 From: Torino 
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QUOTE(Blofeld @ Dec 7 2013, 12:08 PM) The question clearly stated that the p-value is 0.0275 resulted from a two-tailed t-test. This is clearly below 0.05 (5% significance). UserU observed the p-value (0.0275) is higher than the value 0.025 at one side. Shouldn't you should explain clearly to him about the 0.05 significance? So, reject the null hypothesis.  |
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Dec 7 2013, 08:17 PM
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#2
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3,713 posts Joined: Nov 2011 From: Torino
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QUOTE(Blofeld @ Dec 7 2013, 02:09 PM) I think mumeichan does a better job in explaining this. Yeah! mumeichan is the Prince of Statistics in LYN!   |
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Dec 10 2013, 04:18 PM
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#3
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3,713 posts Joined: Nov 2011 From: Torino
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QUOTE(UserU @ Dec 10 2013, 03:19 PM) Second, based on your reply to Blofeld's question: Say, I've used SAS for lab exercises but if I'm answering questions in an exam, I would still have to double the p-value for two-tailed tests? From the attachment below, I can also use either p-value*2 against 0.05 or p-value against 0.025?   |
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Dec 10 2013, 05:17 PM
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#4
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3,713 posts Joined: Nov 2011 From: Torino
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QUOTE(UserU @ Dec 10 2013, 03:19 PM) I would still have to double the p-value for two-tailed tests? Misconceptions about p-value ::(1) p-value ≠ 1 - Φ(|z|) (2) p^-value ≠ 2 × (p-value) p-value made EASY! *****************  For a two-tailed z test, p-value is calculated as p-value = 2*P(Z>|z|) Φ(z) = P(Z ≤ z) where Φ is the Cumulative Distribution Function for the normal distribution P(Z>|z|) = 1 − P(Z ≤ z) = 1 − Φ(|z|) p-value = 2*[1 - Φ(|z|)] |
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