A 14 week age is 2352 hours. Let's assume a province spends 352 hours in fort, which is about 5 full forts over the age, to make it an even 2000 scientist eligible ticks.
A province who runs no laboratories will gain about 70 scientists, if the chance is indeed near 3.5%. A province who runs 20% laboratories for fully half the age (which is not realistic) will gain 35 during his non-lab times, and 43.75 during his lab times, for a total of about 78.75. That's 8-9 additional scientists, on average, at the cost of 20% of your land for half of your non-fort time, which, of course, includes war.