jiyaji110 wrote:
the difference b/w the upper and lower confidence limits is called the confidence interval.
sample of 101 adult male (NY), their mean weight is 72 kg and standard deviation is 15;
then the estimated standard error is therefore 1.5 (standard dev/underroot n-1) then estimated standard error is 1.5 and researcher can state that he is 95% confident that the true mean weight of all adult male (NY) lies between 69 and 75 (as SE is 1.5 and mean is 72 so 95% confidence would be from 69 to 75).
now here comes the point, the confidence interval is now 75-69 = 6 kg.
hope this helps.......
is it SD/squre root n not n-1?
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| Galaxum
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This discussion help me alot.
To SA:
n-1 is ok, and popular for all kind of samples.
you can use n when the sample is big enough..... at that time n-1 is approximate to n
is that right?
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| p53
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If Confidence Interval for relative risk contains 1, then there is no statistically significant effect of exposure (very high-yield and likely USMLE question!). Why? What is the meaning beyond these words?
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| Snood
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Confidence Interval of the "Standard Error Of the Mean"
Mean +/- Z(SD/ squareroot(N) )
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| p53
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You don't get my question.
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| Egypt2000
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p53 , lets first define relative risk. it is a " Comparative Probabilty". So it is the relation between " TWO" probabilties. If it is an exact one, then that means that their is no "Risk". Ok let's back away from abstracting and give an example. Suppose that we have group A 20 people ,they all smoke. 8 of them has ashma. Another group B of 20 persons do not smoke, 4 persons have ashma. Now after conducting a study that concluded that smoking is related to ashma, the next step is to know what is the " Relative risk of developing ashma" so we devide 8/4 and the result is 2 right?..what does that 2 mean?.It means that you are twice at risk to develop ashma if are a smoker compared to a non smoker , you notice the " Comparative probability " here?..now, suppose the study showed that only 4 people had ashma among group A and the same number 4 has ashma among group B, then the relative risk is 1. Which tells that it does not matter if you smoke or not, 4 chances out of 20 you will get ashma regardless. Now apply this to the confidence interval. If your study showed that the relative risk say was 1.4 with a confidence interval of (0.8-2) then that means that your study has no statistical significance because at some point within this range, the relative risk can be 1 which means nothing! or no risk..
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| p53
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Excellent explanation!
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