In this thesis, an experimental and numerical investigation is presented. The capacity of existing probabilistic fracture models when defects in brittle materials are characterized as notches rather than cracks is examined. Fracture toughness is evaluated through experimental fracture toughness testing on single edge bend specimens with pre-fatigued cracks, and on specimens where the crack is replaced with a notch. Finite element models are used to evaluate the mechanical fields. The results from the finite element analysis are used to evaluate the probabilistic models, and finally, the probabilistic model parameters are fitted to the experimental fracture toughness data through parameter optimization. Investigated probabilistic models significantly overestimate the probability of failure when applied to notches.