Calculus/Standard Deviation & Confidence Intervals
I would really appreciate some help with some concepts in stats that I am having trouble grasping. I cannot understand what is meant by 3 standard deviations from the mean. According to my Introductory Stats unit lecture notes, to get a 99.7% confidence interval, you add 3 standard deviations of the distribution to the mean of the distribution but the z-score corresponding to 99.7% is 2.78.
Thanks in advance
First of all, this is not a calculus question...it is statistics. Next time, please
post in that section.
For *any* Normal Distribution, the area (i.e. percentage of area) between any two values
(or the area to the right or left of a value) depends only on the number of standard
deviations away from the mean. So, it does not matter of the mean is 1 or 1000, what
matters is the difference between that mean, the value of interest and the number of standard
deviations away from the mean (a.k.a. z-score).
Check these website for more about it.