So the formula I use is (sample/600) ^ 0.5. ... These large sample size polls now have a comparatively larger weight, and as such Obama’s numbers have dropped a couple points in Texas, ...

I plug these numbers into my formula and get a total sample size of 44, at which point everyone gets excited because this means that we can get the trial done by Christmas, and have our New ...

David A. Schoenfeld, Sample-Size Formula for the Proportional-Hazards Regression Model, Biometrics, Vol. 39, No. 2 (Jun., 1983), pp. 499-503 Free online reading for over 10 million articles Save and ...

Woolson, Bean, and Rojas (1986, Biometrics 42, 927-932) present a simple approximation of sample size for Cochran's (1954, Biometrics 10, 417-451) test for detecting association between exposure and ...

Course TopicsPower analyses and sample size calculations are important parts of many research projects. Often, before data are even collected, it is necessary to calculate and justify the required ...