Conventional software reliability assessment validates a system's reliability only at the end of development, resulting in costly defect correction. A proposed framework employs statistical model checking (SMC) to validate reliability at an early stage. SMC computes the probability that a target system will satisfy functional-safety requirements. The framework compares the allocated reliability goal with the calculated reliability using the probabilities and relative weight values for the functional-safety requirements. Early validation can prevent the propagation of reliability allocation errors and design errors at later stages, thereby achieving safer, cheaper, and faster development of safety-critical systems.