Re: clarify or clogify? re: Why the human race is growing apart

On Sun, 12 Apr 2009 03:26:17 -0700, tgdenning wrote:

Let's do this one first.

2) Direct test scores:

Assume that we begin with a range of integer scores, and there is no
rounding or classification. Then indeed it is *not* highly probable (but
not necessarily zero or very low probability) that groups of half the
population will have the identical mean score.

Right.

Of course, this is not a
realistic scenario, but it seems to be the basis of (your) argument.

I'm not sure what you mean by realistic. If there's a dataset you'd like
to analyze, we could move this into the realm of the concrete pretty
easily.

Also keep in mind the numbers that I was showing you were reals from a
normal distribution. Raw test scores tend to be integers out of a
Poisson, right?

v<-rpois(n=5000, lambda=65)
mean(v)
[1] 64.9058
median(v)
[1] 65

mean(v[1:1000])
[1] 64.775
median(v[1:1000])
[1] 65

mean(v[1001:2000])
[1] 64.905
median(v[1001:2000])
[1] 65

et cetera.



However, in this scenario, I don't see that decreasing SD by increasing
the size of the two samples increases the probability of the two samples
being identical and equal to the population mean, which you and the
other guy suggest.

No -- this might be the misunderstanding. The probability that the
samples are identical probably *decreases* (depending on your data), but
the difference between sample means and the sample mean and the
population mean will also be decreasing.

You seem to be having it both ways if you make that
argument. I am open to correction on this but but you have to make the
case.

You're correct here as far as I can tell.



.

Relevant Pages

  • Quantum Gravity 313.99: 2-Dimensional (in Domain) Maxima and Minima Appear to Relate to Negative
    ... Lehmann (1967-1969 papers in Annals of Probability and/or Annals of ... Readers might ask what exactly Negative Statistical Quadrant ... until we hit that point and then decreases, ... negatives are closely associated on the "opposite sides" of the point ...
    (sci.physics)
  • Re: binomial association measure?
    ... I am using the binomial distribution to assess the probability of a ... I think I can see how pcould be the result of a binomial distribution, ... >two counts or between two probabilities, with some correction. ... Four red balls are on the left; ...
    (sci.stat.math)
  • Re: Shakespeare, monkeys, typewriters
    ... Thanks for the correction of my typo. ... how long would it take just "natural selection" WITHOUT some lead in the sense of a "concept"? ... Apart from your analogy ignoring selection, you also fail to distinguish between the probably of a some result, and the probability of a particulary result. ... That humanity is improbable is only signficant if you introduce a teleological assumption that humanity was the target of the process. ...
    (talk.origins)
  • Re: need help with one problem (sampling )
    ... But I have seen that in case of proportions sometimes they add and subtract 1/2n where n is the sample size. ... probability of ... you go halfway to the ... correction of 1/2n. ...
    (sci.stat.math)
  • Re: Advanced Probability.
    ... that is the probability of "less than or equal to". ... Correction: ... Similarly, in the VB function genprob, change the comparison to: ... first line and press Space and Delete.) ...
    (microsoft.public.excel.worksheet.functions)