# Statistic

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• #34805

Elder
Participant

Does someone know how to calculate the confidence level (in %) from a choosen sample size, with the means and standard deviations of the sample set and entire population known?
(for example, the chosen sample size is 5 and the entire population contain 80 elements, the sample mean is 7 and standard deviation is 1.5; the means and standard deviation for the entire population are 5.5 and 2)
highly appreciated if someone could answer my question.
Jimmy

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#96374

Dr. Steve W.
Participant

standard deviation, what do you need CI for?

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#96376

Gabriel
Participant

Going on with Dr Steve’s concepts, “Confidence Interval” is used when you are estimating a population’s parameter based on what you found in a sample’s statistic.
For example, imagine that there is a population from which you know, by divine revelation, that it is normally distributed and that the standard deviation is 2, but God forgot to reveal the population’s average. If you take a sample of 5 and find the sample’s average of that sample to be 7, you know that the true population’s average will be somewhere arround 7 (the sample’s average is a sample’s statistic that you use as estimator of the true population’s average, which is  apopulation’s parameter). However, it was just a sample, and the true population’s average will be arround 7 but needs not to be exactly 7. The range where you expect the true population’s average to be with some high degree of confidence in called the Confidence Interval for population’s average. In this case, the confidence interval, for a degree of confidence of about 95%, will be Xbar±2*sigma/sqrt(n)=7±2*2/sqrt(5)=7±1.8. That means, based on what you found and what you already knew, you can say with a 95% of confidence that the true population’s average will be somewere between 5.2 and 8.8.
Now, if you already knew that the true population’s average was 5.5, then the true population’s average is 5.5 and no confidence interval applies.

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#96378

Mikel
Member

Dr. Steve,
I know you are a PhD, so some eccentric behavior is expected. Given that, you still need to learn the difference between the subject and the message. The way you post makes you look either 1) arrogant – looks like you are waving a flag saying hey look Dr. Steve is here with his infinite PhD wisdom again, or 2) just plain dumb.
Since your posts don’t really have that much wisdom, I am leaning toward the just plain dumb.

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#96422

Paul Richardson
Participant

You posit that eccentric behavior is universal in those with a terminal educational degree. What premise was employed to speculate such an assumption?

Paul

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#96423

Mikel
Member

experience

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#109058

Goi
Participant

Pls elaborate how to get the answer

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