+ Reply to Thread
Results 1 to 3 of 3

Thread: Design question: proportion explained variance by placebo effect

  1. #1
    Points: 62, Level: 1
    Level completed: 24%, Points required for next Level: 38

    Posts
    5
    Thanks
    1
    Thanked 0 Times in 0 Posts

    Design question: proportion explained variance by placebo effect




    Dear all,

    I have a design question about investigating a placebo effect. Does anyone have a clue how to analyze the proportion explained variance that is due to a plecebo effect in the actual treatment group? So how can one infer the amount of variance in an effect that is caused due to a placebo effect and a threatment effect? Mostly the placebo effect is measured in a different sample right?

    I would love to get your opinion on this.

    regards,

  2. #2
    TS Contributor
    Points: 17,749, Level: 84
    Level completed: 80%, Points required for next Level: 101
    Karabiner's Avatar
    Location
    FC Schalke 04, Germany
    Posts
    2,540
    Thanks
    56
    Thanked 640 Times in 602 Posts

    Re: Design question: proportion explained variance by placebo effect

    The treatment effect is the difference between placebo group and verum group.
    If you want to assess the magnitude of the placebo effect, you need an additional
    untreated control group, AFAIK.

    Or, one could use a longitudinal design and define the placebo effect as difference
    between baseline and endpoint within the placebo group, although this is not quite
    justified (because improvement will often occur even without, or in addition to any
    placebo effects, e.g. because of the natural course or because of regression effects;
    counting this as placebo effect would result in an overestmation of this effect).

    Just my 2pence

    K.

  3. The Following User Says Thank You to Karabiner For This Useful Post:

    maart91 (02-13-2015)

  4. #3
    Points: 62, Level: 1
    Level completed: 24%, Points required for next Level: 38

    Posts
    5
    Thanks
    1
    Thanked 0 Times in 0 Posts

    Re: Design question: proportion explained variance by placebo effect


    Thanks for your response!

    if I understand correctly, the difference between baseline and endpoint can be defined as placebo effect(with additional noise ofcourse). The thing is, I would like to incorporate this into a model defining the mechanism behind a cognitive rehabilitation program. However, this 'placebo'(or in my study the progress due to diaschisis, placebo and spontaneous recovery), is measured in another sample than the threatment effect of course. So If I want to put this in a model, I'm stuck with the problem that there are no data point of this 'placebo' in the sample the model is for. So the proportion explained variance by the waitlist group is not linked to the data points of the threatment effect.

    Do you have some additional thoughts on this?

    regards

+ Reply to Thread

           




Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts






Advertise on Talk Stats