jglover81 I presume you mean the total effectiveness score for each Article?
if so, in SQL this should clear them as they are just a total integer value in the km_affectiveness attribute on each Article:
set km_effectiveness = null
where km_effectiveness is not null
Note I've set them to NULL in the above example (as per OOTB initial state) but maybe you set them to zero instead if you want.
As with any SQL then test this on a copy of your LIVE system (ie DEV or UAT) first.