difficulty in detecting interactions when effects are limited to a small number of groups

[Josh Bugner]

I am working on a study that includes a large number of groups, different doses and control groups. This study involved administering two drugs. The first drug was given as a pretreatment to block the effect of the second drug. There was a significant effect at one dose combination but no significant statistical interaction due to the large number of dose groups that are all the same (control groups and other dose combinations that were not effective). I am interested if anyone has any suggested references in dealing with this issue.

Thank you,

–JB

[Rafael Garcia]

Josh,

Can you please clarify how your groups are structured? Do you have two drugs and varied dosages and that’s the interaction you’re interested in? 

Raf

[Josh Bugner]

Basically I am looking for a reference that addresses the problem of detecting an interaction when most groups are not expected to differ, so that effects are limited to a very few groups among a large number of total groups.

–JB

[Author]

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