[SciPy-Dev] ttest_1samp strange behaviour

[josef.pktd at gmail.com]

On Fri, May 20, 2011 at 4:56 PM, James Bergstra
<james.bergstra at gmail.com> wrote:
> I was trying to make sure that ttest_1samp did what I thought and came
> across the following...
> In [41]: for i in range(10):
>    ....:     print scipy.stats.ttest_1samp([0]*i, 0)

I don't know if this makes sense, variance is zero in your case

try something like

for i in range(2,1000,10): print(stats.ttest_1samp(1e-10*np.random.randn(i), 0))

Josef

>    ....:
>    ....:
> (nan, nan)
> (1.0, nan)
> (1.0, 0.49999999999999956)
> (1.0, 0.42264973081037427)
> (1.0, 0.39100221895577053)
> (1.0, 0.37390096630005898)
> (1.0, 0.36321746764912255)
> (1.0, 0.35591768374958205)
> (1.0, 0.35061666282020748)
> (1.0, 0.34659350708733416)
> Am I interpreting this correctly that the null-hypothesis is decreasing in
> probability as we actually observe it more times??
>
> James
> --
> http://www-etud.iro.umontreal.ca/~bergstrj
>
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