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Thread: Reporting results p > .05 justified?

  1. #1
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    Reporting results p > .05 justified?

    Hi all,

    Recently I did a field study where I investigated recycling behaviour in the office. We did a baseline and post-intervention measurement of the respons rate (i.e. how much of the total amount of a certain type of waste ends up in the right bin?). For 2 x 2 weeks we collected and analyzed all the trash on a daily base, resulting in 10 + 10 (baseline + post) datapoints.

    On four floors we tested interventions to improve reclycling and we compared these to two control conditions. On a small N=20 we found strong effects (Cohen's d > .80). For some effects the p-value was marginally significant (.05-.10) but we still reported those effects. I was taught that if you find strong effects on a small N that are close to being significant, you can assume the effect is actually there. After all, the p-value will automatically decrease when N increases.

    We also reported effects with a p-value between .10-.15 with an explicit diclaimer that these effects should be interpreted with great caution and that a follow-up study is required.

    Someone, however, heavilly criticized us for reporting effects that have a p-value above .05. I personally think that this person is too rigid concerning the p-value considering the small N and the large effects. But maybe I'm wrong and I shouldn't have reported these results.

    Can anybody tell me whether it was justified to report these results or not (also taking into account the disclaimer we used)? Thanks!


  2. #2
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    hlsmith's Avatar
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    Re: Reporting results p > .05 justified?

    "After all, the p-value will automatically decrease when N increases." perhaps it would if you had a random sample representative of the population.

    Here is an idea, just don't use p-values and report all effects along with confidence intervals. P-values can be sample size depend, don't tell you about confidence, magnitude, or direction.
    Stop cowardice, ban guns!

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