[SciPy-Dev] binom_test incorrect behavior in the tails
Yaroslav Halchenko
lists at onerussian.com
Wed Mar 16 14:50:49 EDT 2011
probably due to incorrect pmf computation (which should be symmetric for
p=0.5, but it isn't):
In [78]: pmfs = scipy.stats.binom.pmf(numpy.arange(0,101), 100, 0.5); print pmfs; print pmfs - pmfs[::-1]
[ 7.88860905e-31 7.88860905e-29 3.90486148e-27 1.27558808e-25
3.09330110e-24 5.93913812e-23 9.40363535e-22 1.26277389e-20
1.46797465e-19 1.50059631e-18 1.36554264e-17 1.11726216e-16
8.28636101e-16 5.60922899e-15 3.48573516e-14 1.99848816e-13
1.06169683e-12 5.24603142e-12 2.41900338e-11 1.04399093e-10
4.22816327e-10 1.61072886e-09 5.78398092e-09 1.96152396e-08
6.29322272e-08 1.91313971e-07 5.51867223e-07 1.51252498e-06
3.94336870e-06 9.79043264e-06 2.31706906e-05 5.23209142e-05
1.12816971e-04 2.32471335e-04 4.58105277e-04 8.63855666e-04
1.55973940e-03 2.69792760e-03 4.47287998e-03 7.11073227e-03
1.08438667e-02 1.58690732e-02 2.22922695e-02 3.00686426e-02
3.89525598e-02 4.84742966e-02 5.79583981e-02 6.65905000e-02
7.35270104e-02 7.80286641e-02 7.95892374e-02 7.80286641e-02
7.35270104e-02 6.65905000e-02 5.79583981e-02 4.84742966e-02
3.89525598e-02 3.00686426e-02 2.22922695e-02 1.58690732e-02
1.08438667e-02 7.11073227e-03 4.47287998e-03 2.69792760e-03
1.55973940e-03 8.63855666e-04 4.58105277e-04 2.32471335e-04
1.12816971e-04 5.23209142e-05 2.31706906e-05 9.79043264e-06
3.94336870e-06 1.51252498e-06 5.51867223e-07 1.91313971e-07
6.29322272e-08 1.96152397e-08 5.78398085e-09 1.61072888e-09
4.22816337e-10 1.04399045e-10 2.41900944e-11 5.24602584e-12
1.06170628e-12 1.99840144e-13 3.48610030e-14 5.55111512e-15
8.88178420e-16 0.00000000e+00 0.00000000e+00 0.00000000e+00
0.00000000e+00 0.00000000e+00 0.00000000e+00 0.00000000e+00
0.00000000e+00 0.00000000e+00 0.00000000e+00 0.00000000e+00
1.11022302e-16]
[ -1.11022302e-16 7.88860905e-29 3.90486148e-27 1.27558808e-25
3.09330110e-24 5.93913812e-23 9.40363535e-22 1.26277389e-20
1.46797465e-19 1.50059631e-18 1.36554264e-17 1.11726216e-16
-5.95423185e-17 5.81138699e-17 -3.65137385e-18 8.67140393e-18
-9.44431785e-18 5.57974827e-18 -6.06218405e-17 4.80626902e-17
-1.07373643e-17 -1.97571409e-17 7.03550182e-17 -1.24116201e-17
-2.13170664e-17 -2.03950711e-17 -1.61294131e-17 1.02130998e-18
-1.29934854e-18 4.42998231e-18 2.52619106e-17 -4.68239813e-17
4.14707331e-17 -2.22261445e-17 6.02816408e-17 1.51788304e-18
-3.98986399e-17 2.08166817e-17 -3.46944695e-18 1.38777878e-17
-7.97972799e-17 8.67361738e-17 -4.85722573e-17 2.77555756e-17
1.38777878e-17 -2.77555756e-17 2.77555756e-17 -8.32667268e-17
1.11022302e-16 -5.55111512e-17 0.00000000e+00 5.55111512e-17
-1.11022302e-16 8.32667268e-17 -2.77555756e-17 2.77555756e-17
-1.38777878e-17 -2.77555756e-17 4.85722573e-17 -8.67361738e-17
7.97972799e-17 -1.38777878e-17 3.46944695e-18 -2.08166817e-17
3.98986399e-17 -1.51788304e-18 -6.02816408e-17 2.22261445e-17
-4.14707331e-17 4.68239813e-17 -2.52619106e-17 -4.42998231e-18
1.29934854e-18 -1.02130998e-18 1.61294131e-17 2.03950711e-17
2.13170664e-17 1.24116201e-17 -7.03550182e-17 1.97571409e-17
1.07373643e-17 -4.80626902e-17 6.06218405e-17 -5.57974827e-18
9.44431785e-18 -8.67140393e-18 3.65137385e-18 -5.81138699e-17
5.95423185e-17 -1.11726216e-16 -1.36554264e-17 -1.50059631e-18
-1.46797465e-19 -1.26277389e-20 -9.40363535e-22 -5.93913812e-23
-3.09330110e-24 -1.27558808e-25 -3.90486148e-27 -7.88860905e-29
1.11022302e-16]
On Wed, 16 Mar 2011, Yaroslav Halchenko wrote:
> I am using scipy 0.7.2 in Debian
> could anyone check if following behavior is still in place in the
> current master:
> $> python -c 'import scipy.stats,numpy; print numpy.array([scipy.stats.binom_test(a, 100) for a in [90, 98, 99, 100]])'
> [ 1.53164509e-17 1.60428187e-19 1.66102449e-18 2.16868332e-09]
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