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I personally prefer less arbitrary thresholds for reporting suggestive results, such as reduced FWE correction (say correcting for volume or region p<0.1), or no threshold at all see UnthresholdedEffectMaps. I (MatthewBrett) personally prefer less arbitrary thresholds for reporting suggestive results, such as reduced FWE correction (say correcting for volume or region p<0.1), or no threshold at all see UnthresholdedEffectMaps.

Reporting SPM results at uncorrected p value thresholds

When reporting results at an uncorrected p value threshold, we often want to be able to conclude that the results we see are reliable.

By 'reliable' we often mean the usual 'if the data here is actually random, and I repeated this experiment many times, is there a low (0.05) probability I would see anything at my chosen threshold by chance'.

If that's the reliable you want, then p<0.001 is not useful - you will need a familywise error rate method giving a false positive rate of 0.05, either for the whole volume or corrected for specified volumes of interest.

Of course, with the standard statistical measure of reliability, you run the risk of false negatives, because you have strongly controlled for false positives. If you want to be able to report results that are not reliable in the standard statistical sense, but suggestive, then one option is to use a lower statistical threshold. I don't think p<0.001 has much to recommend it as a lower threshold, as it has an arbitrary relationship to false positive / false negative trade-off that will depend on the characteristics of your data.

I (MatthewBrett) personally prefer less arbitrary thresholds for reporting suggestive results, such as reduced FWE correction (say correcting for volume or region p<0.1), or no threshold at all see UnthresholdedEffectMaps.

CbuImaging: UncorrectedThreshold (last edited 2013-03-07 21:23:04 by localhost)