i can do this on a online calculator, but when im doing it myself its total differnt answer
whast standard deviation for these
10,11,11,12,12,12,13,13,13,13,13,13,14,14,14,14,14 ,14,14,14,15,15,15,15,15,15,15,15,15,15,16,16,16,1 6,16,16,17,17,17,17,17,18,18,18,19,19,19,19,20,20
Ive got mode =15
mean =15.18
median =15
some one help me do the standard deviation pleaee.. know this takes time, ive been doing it last 6 hours none stop and cant do it
thanks
Hey gary147.
Its a lot better if you use a computer for data that is this big in terms of observations.
If multiple packages give the same answer, then that should be evidence that you entered in the data correctly and used the right commands.
The definition of "standard deviation" is the square root of the expected value of the square of the difference from the mean. That is, [tex]\{x_i\}[/itex] is the set of numbers, and there are n numbers in the set, the mean is, of course,.
The "variance", the square of the standard deviation, is. And then, of course, the standard deviation is the square root of that,
You may have seen a simplified formula in you text: for any i,so that
^2= \sum_{i=1^n} x_i^2- 2\mu x_i+ \mu^2= \sum_{i=1}^n x_i^2- 2\mu\sum_{i=1}^n x_i+ \mu^2\sum_{x=1}^n 1)
+ \mu^2(n))
and once we have divided by n,
. That is simpler to use because you can go ahead and keep a running sum of both
and
and the same time, determining
later.
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