Testing Your AILeave-One-Out Cross Validation (LOOCV)
How far can we push k? With 20 farms, the most folds we can make is 20 — one farm per fold. This is leave-one-out cross-validation (LOOCV): . Each round trains on 19 farms and tests on the single farm left out (the amber ring). Complete both missions.
Each validation "exam" is now just
Note
LOOCV trains as many models as there are rows. For 20 farms that is nothing; for 1 lakh photos it means training 1 lakh models. So leave-one-out is used only on small datasets, or for models with a mathematical shortcut.