When analyzing reliability, it's important to consider epistemic uncertainty caused by lack of information. Different methods like probability, combined distribution, interval analysis, and evidence theory can be used to handle this uncertainty. Probability method is best if you know the input variables' probability distribution, while interval method is better if you have no information about it. Combined distribution method is not recommended as it only provides the average failure probability. Evidence theory falls between probability and interval methods, becoming more like probability with detailed probability assignment. However, it has the highest computational cost among the methods compared.