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Re: Standard Deviation Question
From: Bill B
Date: 2013 Jan 04, 22:54 -0500

```On 1/4/2013 8:10 PM, William Hawes wrote:
> Not being a math wiz, when should I be using stdDevPop and when should I
> be using stdDevSamp? The TI-Nspire Reference Manual does not shed any
> light on when to use the two different Standard Deviation functions. Can
> anyone elaborate?

This should be fun if the heavyweights join in.  My math is limited to
Purdue U. calculus and statistics as they apply to undergrad
consumer/market research.

Alex (a world-class mathematician) has posted results for relatively
small samples in both n-1 (sample) and n (population). If I recall
correctly I queried him personally as to what was a sample and what was
a population and he suggested that it is a tough call.

An example from a text (Statistics for Dummies) uses an example of
taking a measurement of every child in a teacher's first-grade home
room. Following what I believe Alex was trying to impart to me: It could
be a population as it is all the kids in the home room (unless one was
home sick). More than one first-grade home room in the school, maybe it
is a sample of the school. Is it a sample of all the first-grade
homerooms or all first graders in the nation?

At least that's what I came away with--a slippery slope. Hopefully Alex
will jump in and clear up my fuzzy interpretation.

As per coin flips or sextant observations etc. there could be in theory
be an infinite number so anything is just a sample.

Personally I tend to treat 5 or 10 observation as a sample but run the n
(population) anyway. The deviation is smaller and makes me feel all warm
and fuzzy ;-)

Bill B

```
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