Probability of the proposed K2-18c periodic signal P_c = 8.962 days existing within the CARMENES RV dataset from S18 but with a single measurement omitted via leave-one-out cross-validation. The abscissa depicts the observation epoch of each omitted RV measurement. The solid horizontal line depicts the 1σ dispersion of the probabilities. The three measurements which lie above the 1σ line significantly suppress the probability of P_c and are henceforth treated as anomalous.