This may really be nitpicking... but how would you best phrase this sentence (the context is a scientific paper)?
[parameter] was measured in the presence or absence of [drug name].
[parameter] was measured in the absence or presence of [drug name].
The first one sounds better to me, but I cannot say why, nor I would say the second is wrong...
EDIT: to better clarify, I have control experiments where the parameter was measured without drug and other experiments where it was measured in its presence.