File:Quantile meta test.svg

Summary

Description
English: Normal quantile plot of test statistics in which the upper tail is heavier than standard normal but the lower tail is not. The red point falls at 3.13,2.06 and the blue point falls at -1.75,-1.96.
Date
Source Own work
Author Skbkekas
SVG development
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Source code
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Python code

import numpy as np
import matplotlib.pyplot as plt
import scipy.special as sp

## Simulate test statistic values.                                              
T = np.random.normal(size=200)
T[0:20] = np.random.normal(size=20)+2
T = np.sort(T)

## Standard normal quantiles.                                                   
P = np.arange(1, 201, dtype=np.float64)/201
Q = sp.ndtri(P)

plt.clf()
plt.grid(True)
plt.plot([-4,4], [-4,4], '-', color='grey')
plt.hold(True)
plt.plot(T, Q, 'o', color='black', ms=3)

print T[196],Q[196]
print T[4],Q[4]

plt.plot((T[196],), (Q[196],), 'o', color='red')
plt.plot((T[4],), (Q[4],), 'o', color='blue')

plt.xlabel("Observed test statistic quantiles")
plt.ylabel("Standard normal quantiles")
plt.savefig("quantile_meta_test.png")
plt.savefig("quantile_meta_test.svg")

Licensing

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Category:Q-Q plot
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