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April 8th, 2013, 02:50 PM   #1
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none in +/- 2 standard deviations

I have for sample:
Quote:
50.98
48.8
65.18
69.64
28.22
102.74
72.59
114.56
81.96
66.2
95.08
120.58
71.98
36.69
Although it's small and I'm inexperienced, I'm wondering why there's nothing outside (+/-) 2 standard deviations (2?), which is 55.34 (? = 27.67) on the mean (?) 73.23 ; the range is < 17.89, > 128.57.

I think ? would be smaller so there is something in that range (+/-2?). Or perhaps there's some concept I don't understand which would make it possible for the whole sample to be limited in 1?.
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April 9th, 2013, 12:01 PM   #2
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Re: none in +/- 2 standard deviations

2? is the bound for approximately 95% of a sample. Since your sample size is 14, it is not surprising that they are all inside this range.
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April 9th, 2013, 02:39 PM   #3
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Re: none in +/- 2 standard deviations

Thanks. At least I know it's not erroneous but it's weird for me to understand. Well I guess it's hard to have 1/20 in the range when there's not even 20 items. I didn't think about it that way.
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April 9th, 2013, 02:43 PM   #4
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Re: none in +/- 2 standard deviations

Darn! I can't edit my last post. Well this is its PS.

Quote:
Originally Posted by DynV
Or perhaps there's some concept I don't understand which would make it possible for the whole sample to be limited in 1?.
I don't know if I was confused thinking the samples was limited in 1? or I was confused writing it, thinking of 2?.

Anyway I'm not concerned about the issue anymore.
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