I've been running some GLMs using a stepwise backwards deletion routine (main effects, 2 way, 3 way), deleting the least significant terms between each repeat.

I've found some significant interactive terms and just wanted to check that my interpretation of what these mean is correct....

+ if two terms show a significant positive interaction then it means that an increase in one of these terms significantly relates to an increase in the strength of the effect of the other term?

- if two terms show a significant negative interaction then it means that an increase in one of these terms significantly relates to a decrease in the strength of the effect of the other term?

what does it mean if there is a significant 3-way interaction?

as ever, many thanks

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