it's been EW and Margie claiming that the SD will change:
Sigh...
Let's say scores of the sample are
18 <---WB's ^_^ 84 78 74 79 96 35 78 85
sample mean (simple average) = 69.66....
standard deviation = 25.61738
Let's take out WB's score. This gives us:
sample mean= 76.125
standard deviation = 17.91597
Well lo and behold, while the average did increase by taking out WB's IQ score, the standard deviation ended up decreasing. This was because WB's sore was so low that it taking it out made the distribution more clumped together which results to less variability which means less sd. That is why you can't say that a sample's average score would increase/decrease by a standard deviation when you take out an element of that sample. It's not right to use sd in a sentence such as:
the collective IQ of the readers of this board would increase by at least one standard deviation through the implementation of fae's suggestion.
This was what I meant, nothing more, nothing less.
Just had to comment, my inner statistician was screaming murder. >.< Anyway, you can still have the last say after this post. :) Be my guest. :D