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Repeated-measures statistics: number of trials or number of steps?

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  • Repeated-measures statistics: number of trials or number of steps?

    We might envision a repeated-measures design with multiple sprinting trials for each condition (no fatigue assumed). Correlated measurements would be expected, so we need to employ a repeated-measures test. The expectation is that multiple trials helps us arrive at a value that is closer to 'reality'.

    However, what if each sprinting trial involves multiple steps (peak forces following contact, for example)? The measurements corresponding with each step would also be correlated within each trial. Since there is an expected improvement in statistical power when we employ a repeated-measures design, how can we take advantage of multiple steps?

    Another example might be calculating average values over of some measure the entire gait cycle from running trials collected for 1 minute. At 90 strides/180 steps per minute, that is a lot of measurements. It would seem that we would fail to benefit from statistical power considerations if we simply put one single average value from that 1 minute trial into the hypothesis test calculations.

    Conceptually or otherwise, is there such a thing as a within-trial factor nested inside a within-subject factor?

  • #2
    Re: Repeated-measures statistics: number of trials or number of steps?

    Hi Timothy,

    I am not an expert in this area, but it seems to me that if you take averages of steps, or peak values from each step you have created discrete values which can be treated as repeated measures - though a large amount of repeated measure could be difficult to process.

    If you consider a continuous signal, time series analysis would be more appropriate. You might find an approach outlined in the following article interesting https://www.mdpi.com/1099-4300/20/10/764/htm

    Regards
    Dan

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