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Thread: Crossover design or Randomised Block Design?

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    Question Crossover design or Randomised Block Design?




    I have two groups of rats (group A and group B).
    'Pretreated' means they were injected beforehand (with either memantine or saline). They were then injected (with either baclofen or saline) again after 15 mins. Saline is the control.

    Day 1
    Both groups are pretreated with memantine

    Then, after 15 mins:
    - Half of Group A is given saline (Group A1), the other half is given baclofen (Group A2)
    - Half of Group B is given saline (Group B1), the other half is given baclofen (Group B2)

    Day 2
    Both groups are again pretreated with memantine

    Then after 15 mins:
    - Group A1 is given baclofen (was given saline on Day 1), Group A2 is given saline (was given Baclofen on Day 1)
    - Group B1 is given baclofen (was given saline on Day 1), Group B2 is given saline (was given baclofen on Day 1)

    Day 3
    Both groups are pretreated with saline

    - Group A1 is given saline, A2 is given baclofen
    - Group B1 is given saline, B2 is given baclofen

    Day 4
    Both groups are pretreated with saline

    - Group A1 is given baclofen, A2 is given saline
    - Group B1 is given baclofen, B2 is given saline

    I am seeing whether memantine has an effect on feeding on the rats.
    I measured their food intakes after their treatments.

    My question is whether this is a crossover design? I just want to make sure that it is.

    (For those wondering: baclofen and memantine are drugs).
    Last edited by gunwind; 12-20-2013 at 12:50 PM.

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    Re: Crossover design or Randomised Block Design?

    There is definitely a crossover into all four arms. Not sure you need to call them A and B, why not A, B, C, D? Is one day a sufficient enough washout period. If I eat more on day one will I eat less the next day regardless of the subsequent intervention? Rat satiety is not my forte, just a question.
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    gunwind (12-22-2013)

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    Re: Crossover design or Randomised Block Design?


    Quote Originally Posted by hlsmith View Post
    There is definitely a crossover into all four arms. Not sure you need to call them A and B, why not A, B, C, D? Is one day a sufficient enough washout period. If I eat more on day one will I eat less the next day regardless of the subsequent intervention? Rat satiety is not my forte, just a question.
    Thanks very much for responding

    The reason why I called them A1, A2, B1, B2 is because these same rats underwent a previous experiment, where A + B were all given saline and C + D were all given memantine. However that was a separate experiment, so I could change it to your suggestion of A, B, C, D for this cross over design.

    You are right, one day is not a sufficient washout period, so that is one valid criticism of this experiment.

    Do you know if crossover designs usually have four arms or two arms?
    With this in mind, should I be comparing the results of all four groups against each other? Is this the usual statistical procedure?
    Last edited by gunwind; 12-22-2013 at 07:21 PM.

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