I want to conduct a four arm study using the SWE method if
possible.The study is as follows. The patients are given Item A for
four months then randomised to four possible arms. First arm the
patient is examined and a response of 55% is expected. The second arm
, the patient is given a Item B for a further four months and a
response rate obtained (let us say 70 %) Third Arm a patient is given
Item C  for four months and a reponse rate obtained (say 80%) Finally
a patient in the fourth arm is given Item D and then examined after
four months and a response rate is obtained. (expected response 90%).
How many patients do I require? Please give a flexible response as the
percentages given above are approximate.