Seminar aus Statistik für das Magisterstudium - Example 7.4

From StatWiki

The following data are given by Moss et al (1992) for the somatostin-immunoreactive cell density before and after eradication of H. Pylon using DeNol. If a new cross-over study was planned with 15 patients, what effect size could be detected with 80% power and 2-sided 5% significance?

comb = expand.grid(power=c(.8,.9),alt=c("one", "two"))
data.frame(comb, 
           n=apply(comb, 1, function(r) 
                               ceiling(power.t.test(delta=10, 
                                                    sd=10,
                                                    power=as.numeric(r[1]), 
                                                    type="paired", 
                                                    alt=r[2])$n)))

#

  power alt  n
1   0.8 one  8
2   0.9 one 11
3   0.8 two 10
4   0.9 two 13