= Margaret M. Hilferty
{c}
<Margaret M. Hilferty> coauthored the 1931 paper <The Distribution of Chi-Square by Edwin B. Wilson and Margaret M. Hilferty>. The original byline identifies her with Harvard's Department of Vital Statistics; no fuller personal name is inferred from the initials.<The Distribution of Chi-Square by Edwin B. Wilson and Margaret M. Hilferty>[Original title page, p684]{ref}
Their <Wilson-Hilferty transformation> reduces the skewness of a <chi-squared distribution> by taking a cube root. For $X\sim\chi_k^2$, the standardized quantity $((X/k)^{1/3}-(1-2/(9k)))/\sqrt{2/(9k)}$ is approximately standard normal. It provides a practical approximation to quantiles and tail probabilities, with accuracy depending on the <statistical degrees of freedom> and the probability region.<The Distribution of Chi-Square by Edwin B. Wilson and Margaret M. Hilferty>[Cube-root approximation, pp684–688]{ref}
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