Show how to obtain sample size.

SamPle-size assumptions were based on previously published data.5:9 Assuming a mean [iSD} number of ventilator-free days of 12.71106, we estimated that a sample of 524 patients would need to be enrolled in order for the study to have 80% power, at a two-tailed signicance level of 0.05, to detect a mean between-group difference of2.6 ventilator-free days. On the basis of data from the Pulmonary Artery Catheters in Management of Patients in Intensive Care [PAC-Man] trial, we estimated that the study-withdrawal rate would be 3%,11 and we therefore calculated that the study required a total 0540 patients. Show how the authors obtained the required sample size for their trial i.e. show how the assumptions about mean values and standard deviation quoted in the sample size paragraph in the Methods section give rise to the sample size that was adopted. (You may use an appropriate formula or just use a software command, as long as you explain why it is appropriate.)