keywords Best linear unbiased estimator Burned-in systems COHERENT SYSTEMS COMPONENTS Coherent system D-spectrum Dynamic reliability Dynamic signature Engineering Engineering, Industrial Exchangeability Hazard rate ordering Likelihood ratio ordering Mixed system Nonparametric inference Operations Research & Management Science Order statistics Parametric inference Proportional hazard rate model RELIABILITY Science & Technology Signature Stochastic ordering Systems with shared components Technology k-out-of-n system