They won’t be perfect. I planted the control plot of potatoes one month later than the olla plot. And the control cucumbers were inside the house for an extra week, where they got a head start on flowering.
It won’t be rigorous. I’m not going to measure how much water I use for olla plots vs control plots.
What I will do is water the control plot and fill ollas as needed. And I will compare how the plants fare and their productivity. If the olla plots do even just as well as the control plots, they will be a huge success cause they will have been much less work (and less water) than the traditional plots.
Potato Olla Plot
Potato Control Plot
Cucumber Olla Plot
Cucumber Control Plot
UPDATE: Read the end-of-season retrospective on ollas by potato!
Sustainable Scientist 
If nothing else, they are truly nifty garden ornaments!