Hi, power.t.test works for some range of input parameters but fails otherwise.
> power.t.test(delta = 0.5849625, sd=0.1, power=0.8, sig.level=0.05)$n [1] 1.971668 > power.t.test(delta = 0.5849625, sd=0.05, power=0.8, sig.level=0.05)$n [1] 1.620328 > power.t.test(delta = 0.5849625, sd=0.01, power=0.8, sig.level=0.05)$n Error in uniroot(function(n) eval(p.body) - power, c(2, 1e+07), tol = tol, : did not succeed extending the interval endpoints for f(lower) * f(upper) <= 0 In addition: Warning message: In qt(sig.level/tside, nu, lower.tail = FALSE) : NaNs produced I guessing that sd is very small compared with delta, hence the problem. But what are allowed values (ratios) of delta and sd? Best Witek -- Witold Eryk Wolski ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
