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Appendix 3: Significance of a
Chi-Square Statistic
For 30 or fewer degrees of freedom, an exact series expansion is used; otherwise
the Peizer-Pratt approximation is used.
Notation
The following notation is used in this appendix:
X Value of the chi-square statistic
k Degrees of freedom
Q Significance level (right-tail probability)
Computation
• If X≤0 or k<1,
Q=1
• If k=1,
QQ X
N
=249
where QX
N49
is the standard normal one-tailed significance probability.
• For k≤30 , an exact series expansion is used (Abramowitz and Stegun, 1965,
eqs. 26.4.4 and 26.4.5)
