Thus, if Rebif reduced relapses by 30%, Campath would have reduced them by 56,1%. The relative difference between 56,1% and 30% is 87% ((56,1-30)/30x100=87).
I dont agree with your numbers finn, and Rebif has a generally accepted (ie derived from previous large studies) effectiveness of around 30% (i think for relapses, not for disability progression, but thats another misalignment in all our calcs). However, assuming 30% is right. And there were no anomolies such as there actually were with people coming off of treatments etc etc etc The simple maths in my eyes is:
Rebif is 100%-30% = 70% Not effective.
Campath is 88% more effective (from the results), so Campath would be:
70 % * (100 - 88)/100 = 8.4% ineffective
Therefore, 100-8.4 = 91.6% effective by my math, which also sorta aggrees with what Ian has been told ie around 95%.
The trick to remember in the maths is that Campath is working on the numbers that Rebif failed on (ie the 70% and not the 30%)
Or, by example, if we have 200 people in the study (100 on each treatment), 70 people on rebif would of "failed" while only 8.4 people on Campath would of "failed". Giving the final figure of 88% via, 100 - (8.4 / 70) = 88% where we are comparing the numbers of those that failed (ie 8.4 to 70)
NB: I know there are a LOT of assumptions, simplifications and crossing of numbers in the above.