Thanks for going to some trouble. One point about any one actigraphy instrument not being fully accurate is that one is interested in comparing it with itself i.e. one isn't using one device at the start of the trial and another device at the end of the trial. Another point about the actigraph figures is that one is dealing with big numbers. Unfortunately different studies use different figures but if one takes the Friedberg 2009 study: 224696.90 before the treatment; 203916.67 after. The smallest change on the SF-36 is 5 points or 5% of the score (which would translate to a change of 10% or more on initial scores of 50 or less).