+ Reply to Thread
Results 1 to 3 of 3

Thread: comparing two groups with binary data

  1. #1
    Points: 4, Level: 1
    Level completed: 7%, Points required for next Level: 46

    Posts
    1
    Thanks
    0
    Thanked 0 Times in 0 Posts

    comparing two groups with binary data




    Hi,

    Suppose I am testing two drugs, I and II. The response profile is either I >II, II<I or I == I. I was trying to figure out the best way to do this.

    One way I thought of was to throw out all the ties (I == II), and then assign a 1 where I>I and a 0 I<II. Then this boils down to a binomial distribution (which I can approximate with the normal).

    But I was wondering if throwing away the ties is really appropriate... If I don't throw away ties, I can't use the binomial distribution (so would I switch to some multinomial test)?

    The other thing I can think of is some wilcoxon rank sum test or mann whitney u test with ties... but I was wondering if anyone else has an idea? The concern here is that there will be a LOT of ties...

    Thanks!
    Last edited by greeniguana; 08-15-2013 at 10:15 PM.

  2. #2
    Points: 3,057, Level: 34
    Level completed: 5%, Points required for next Level: 143

    Posts
    2
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: comparing two groups with binary data

    Hi greeniguana,

    could you be more specific about the research question and design? Are the scores independent or dependent? This will be important for the appropriate test. If the scores are dependent you could use a Wilcoxon signed rank test which will exclude all ties. In the other scenario you could use a Mann-Whitney but I don't have in mind how it will treat ties.

    Regards,

  3. #3
    Omega Contributor
    Points: 38,374, Level: 100
    Level completed: 0%, Points required for next Level: 0
    hlsmith's Avatar
    Location
    Not Ames, IA
    Posts
    6,998
    Thanks
    398
    Thanked 1,186 Times in 1,147 Posts

    Re: comparing two groups with binary data


    Yes, please describe the formatting of variables in detail and your hypothesis. Are both drugs used on the same person or are there two groups, are you wanting to test the non-inferiority, inferiority??
    Stop cowardice, ban guns!

+ 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