Doubt in Range(X)

[jman...@gmail.com]

Hi,

I have a question about what is happening in this video at 00:05:09 -

http://www.youtube.com/watch?v=BGXmy4vA0R0#t=309s.

Why range of X is interpreted as subset of (mean-SD,mean+SD) but not as (mean-k*SD, mean*K+SD) for some k in R? Like why we assume k to be 1? That I have not understood. Please clarify this..

Thanks!

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