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Help regarding bootstrap technique

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  • Help regarding bootstrap technique

    Hello Colleagues,

    I am a new user/reader in the Biomch-L list and have a question regarding
    the application of bootstrap techniques to in vivo force measurement/gait
    analysis data. Let me explain the data set I am dealing with and then ask
    my question...

    We have directly measured the in vivo forces (using implanted force
    transducers) in a certain muscle-tendon unit of a quadruped (n=3 animals;
    say N1, N2, N3) for different levels of activity (say A1, A2, A3). For each
    activity level within an animal we have several repeated measurements of the
    response variable, which may be different from each other, i.e.:

    N1 R11 R12 R13
    N2 R21 R22 R33
    N3 R31 R32 R33

    where the Rij's (the number times a measurement is repeated) are not
    necessarily equal. Further, we have three classes of response variables and
    the ranges of Rij's for the three corresponding data sets are 8-10, 15-30,
    and 1200-1500.

    We are interested in finding out if changing the activity level (i.e.
    subjecting the animals to activity A1 vs A2 vs A3) has an effect on the
    response variables. Using the GLM (generalized linear model) procedure in
    SAS, we performed ANOVA on our data and were able to state that changing
    activity level significantly affects several of the response measures.

    We submitted our data for publication and the study was received very well
    by the reviewers. One of the reviewers, however, said that the statistical
    analysis was inadequate because of a low sample size and suggested we review
    and apply the bootstrap technique to evaluate our data.

    Now, I only have a very rudimentary knowledge of the bootstrap and the Monte
    Carlo techniques, all of which I have gleaned from reading through a section
    on Bootstrapping and Monte Carlo Simulations in the "Numerical Recepies"
    book. I did a literature review on bootstrap on medline and found only one
    paper as applied to gait analysis (Sutherland et al, 1996) and was unable to
    discern from it as to how to apply the technique to our data.

    So here are the questions/requests I have:
    1. How would it be useful to apply the bootstrap technique to analyze
    our data? How will it help increase the confidence in our conclusions that
    activity has a significant effect on various measures of in vivo force?
    2. Can you guide me to a publication(s) which I can read through (and
    perhaps further discuss with you) to help me formulate how to use this

    Many thanks. As usual, I will summarize the replies I get.

    I look forward to numerous replies (hopefully!)


    Prasanna Malaviya, Ph.D.
    Georgia Institute of Technology
    Atlanta, GA
    (404) 894-2212, Fax: (404) 894-2291

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