Dr. su was conducting a study on a new antidepressants. Half of the participants were given the new drugs and the other half were given placebo. what procedure did Dr. su use to treat both groups excatly the same and not inadvertently influence the results

"six months ago, several of molly's friends joined the trimtime fitness center. each of them participated in trimtime's weight-reduction and fitness regimen. all reported substantial weight reduction, and all are visibly slimmer. molly is convinced. she joins trimtime and enrolls in the program, hoping and expecting to see the same results. she is especially delighted to learn that trimtime had adjusted its program to make it even more effective in a shorter period of time." what is the feature in question/attribute of interest in this argument?