I don't know the formulas off the top of my head or whatever but try dividing the stddev by sqrt(n) or something. Basically find the standard ERROR not the standard DEVIATION.
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senorhousemouse
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WhoopsyDaisy 03/05/12 4:16:00 PM #1: |
I don't know the formulas off the top of my head or whatever but try dividing the stddev by sqrt(n) or something. Basically find the standard ERROR not the standard DEVIATION.
-- senorhousemouse ... Copied to Clipboard!
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Menji76 03/05/12 4:17:00 PM #2: |
I'm prepping for an exam and I can't seem to figure out how to calculate the P-value when you're comparing two samples in Difference Between Two Means and Comparing the Means of Two Related Populations.
I can find the t statistic and confidence intervals fine but one of the practice questions asks for the P-value. And whenever I look up how they do it in the book, they say they plugged it into Excel which we can't use... so I look back to how they original calculate it and they find the z-stat first. But finding that requires: x-mu / stan dev or xbar - mu / stan dev / sqrt(n) I only have sample data and not population mean or population standard deviation. I tried estimating it using the sample numbers but I'm not getting the same answer as the book gives. Help? -- Menji - Sign My Petition for "Search By Username" http://www.gamefaqs.com/boards/7-site-suggestions/55168396 ... Copied to Clipboard!
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masterplum 03/05/12 4:22:00 PM #3: |
Oh Boy. I came in 12th in the state in stat but that was Years ago.
If you only have the sample data and not the population data I don't think you even can find the one you are looking for. Doesn't one test go with Population and another for sample size? Are you sure you need the P value then? Are you sure you need to know that for your exam? -- yE frE me Kweku Ananse Papa me:http://img235.imageshack.us/img235/1508/masterplumgm3.jpg ... Copied to Clipboard!
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Menji76 03/05/12 4:34:00 PM #4: |
Well it's one of the questions he said to practice.
Let me explain this more in depth. I'm comparing the means of two related populations: Seven patients, we have their before and after data numbers for their blood. 1 - 158 - 284 2 - 189 - 214 3 - 202 - 101 4 - 353 - 227 5 - 416 - 290 6 - 426 - 176 7 - 441 - 290 The first part was at .05 significance, is there evidence that the mean is higher before than after the transplant. I did not reject the Ho because my tstat was 1.84 which was < 1.94 from DoF = n-1 at .05 Then they ask for the p-value which the back of the book gives as 0.0575. I have no idea how they get this. Also, I might be confusing my variables. sigma = sample st dev and s = pop st dev, correct? I just don't know what to use for mu in the Z stat equation since I don't have that. -- Menji+ What Will Never Be the Greatest. http://img85.imageshack.us/img85/8184/ffxiii.gif ... Copied to Clipboard!
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Menji76 03/05/12 4:38:00 PM #5: |
oh and I am using stand dev variables backward
-- Menji - www.last.fm/user/menjii You got to put me on. Come on! Come on! ... Copied to Clipboard!
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WiggumFan267 03/05/12 4:39:00 PM #6: |
maybe but its probably been too long
-- ~Wigs~ New York FOOTBALL Giants: SUPER BOWL XLVI CHAMPIONS ... Copied to Clipboard!
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WiggumFan267 03/05/12 4:41:00 PM #7: |
From: Menji76 | Posted: 3/5/2012 7:34:26 PM | #004 this is backwards I believe -- ~Wigs~ New York FOOTBALL Giants: SUPER BOWL XLVI CHAMPIONS ... Copied to Clipboard!
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Menji76 03/05/12 4:41:00 PM #8: |
too slow wigs
-- Menji "I'm on a f***ing bicycle ding ding ding." ... Copied to Clipboard!
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Ness26 03/05/12 4:44:00 PM #9: |
I think you have to reverse the table, basically. Find what significance corresponds to the t-value you got. You probably have to interpolate.
-- No amount of planning will ever replace dumb luck. ... Copied to Clipboard!
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