Tweedie's Formula and Selection Bias

RAND Statistics Seminar Series

Tweedie's Formula and Selection Bias

Presented by Dr. Bradley Efron—Stanford University

Thursday, March 1st, 2012
10:30 a.m. – 12:00 p.m. PT / 1:30 p.m. – 3:00 p.m. ET
Conference Room TBA
RAND Corporation, Santa Monica, CA

Please contact Fabiola Lopez if you would like to attend this seminar.


Suppose the statistician observes some large number of estimates z[i], each of which is unbiased for its unobserved true mean mu[i]. The largest say 10 of the z[i]'s are likely to substantially overestimate their corresponding mu[i]'s, this being "selection bias", or "regression to the mean". Tweedie's formula, first reported by Robbins in 1956, offers a simple empirical Bayes approach for correcting selection bias. I will discuss its merits and limitations, in terms of some examples and a little bit of theory relating to the James-Stein estimator. The theory concerns the use of "indirect information" for statistical inference.

Speaker Bio

Dr. Efron, the Max H. Stein Professor and Professor of Statistics and of Health Research and Policy, is a recipient of the National Medal of Science. He previously had been awarded the Ford Prize, MacArthur Prize, and the Wilks Medal and has served as president of the American Statistical Association and of the Institute of Mathematical Statistics. Dr. Efron's work has spanned both theoretical and applied topics, including empirical Bayes analysis, applications of differential geometry to statistical inference, the analysis of survival data, and inference for genetic data.

Attending a Seminar

Other Locations/Times:
Washington, D.C. Conf. Rm. 4132: 1:30 p.m. ET
Pittsburgh Conf. Rm. 5202: 1:30 p.m. ET

RAND visitors are welcome to attend and must RSVP at least one day prior to the seminar. To ensure your attendance please contact Fabiola Lopez at with your name, company (or university) affiliation, and national citizenship (for security purposes).

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For further information and to be added to the mailing list contact Fabioloa Lopez at