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Statistics course and homework discussion. Elementary statistics.enSat, 31 Jan 2015 17:39:40 GMTvBulletin60http://www.talkstats.com/images/misc/rss.pngStatistics Help @ Talk Stats Forum - Statistics
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Performing a Paired T test
http://www.talkstats.com/showthread.php/59375-Performing-a-Paired-T-test?goto=newpost
Sat, 31 Jan 2015 04:39:33 GMT239 subjects had their cholesterol measured, and then were put on high-fiber diets. After a month on the high-fiber diet, the cholesterol was... subjects had their cholesterol measured, and then were put on high-fiber diets. After a month on the high-fiber diet, the cholesterol was measured again. The mean LDL cholesterol level before the experiment was mg/DL. The mean level after the subjects were on a diet for a month was mg/DL. The sample standard deviation of the amount of cholesterol each patient lost was mg/DL.
(a) Test whether or not the high-fiber data significantly reduced the LDL cholesterol level at an α = 0.05 level.
For this one I just used a paired to test. The hypothesis are and . We see that . It follows that Thus we reject the null hypothesis

(b) If the true reduction in cholesterol was 10 mg/DL, what is the power of this test?

We assume that . Since is large we can use a normal approximation. Thus it follows that . Also we shall assume that is approximately . Thus Power

. This is what I get for part b. I think it looks right but im not entirely sure. I'm basing the rejection region off of part (a) that is reject the null hypothesis as long as the T statistic is greater that . Thanks :cool:
]]>Statisticsraidernationhttp://www.talkstats.com/showthread.php/59375-Performing-a-Paired-T-test<![CDATA[Adding the mean to a set of scores doesn't change it. Why?]]>
http://www.talkstats.com/showthread.php/59370-Adding-the-mean-to-a-set-of-scores-doesn-t-change-it.-Why?goto=newpost
Fri, 30 Jan 2015 18:40:44 GMTHello everybody! I am very happy to have found this forum. I am working away with my undergraduate research methods courses. I am not very good at...Hello everybody! I am very happy to have found this forum. I am working away with my undergraduate research methods courses. I am not very good at it, but I work very hard :yup:

I have a question regarding something I read in my textbook. The textbook said that if you had collection of scores, included the mean (so you have {score1, score2, score3, ... ,scoreN, x-bar} and recalculated the mean in that new set, the original mean does not change. And it's true!

I tried to ask my professor to show me why but all he was able to come up with was something like "Oh yes, it does not add anything so that's why it does not change" but was unable to show me with numbers or symbols.

I have been trying this for a few days and it's driving me crazy. I feel like it's simple enough for me to get it but I can't :(

Here's what I've tried so far. Let's call the scores x and the mean xbar

(X1 + X2 + X3 +...+Xn/n) + Xbar.

(X1 + X2 + X3 +...+Xn)+ (X1 + X2 + X3 +...+Xn/n)/ n+ 1 (<-- because now I have the mean there so I need to increase the denominator by 1)

I tried associating them to see if something would cancel out like:

but now I'm stuck. Nothing falls out of the equation like I expected it.

Any help, please?

Thank you for your time!
]]>StatisticsSuzy46http://www.talkstats.com/showthread.php/59370-Adding-the-mean-to-a-set-of-scores-doesn-t-change-it.-Why<![CDATA[What is pillai's trace value?]]>
http://www.talkstats.com/showthread.php/59368-What-is-pillai-s-trace-value?goto=newpost
Fri, 30 Jan 2015 12:11:06 GMTDear fellows,
I stumbled on this using the software Gpower,
Doing some basic research I cannot really understand what exactly is!:confused:
...Dear fellows,

I stumbled on this using the software Gpower,
Doing some basic research I cannot really understand what exactly is!:confused: