Limited Fluctuation Credibility for Exam STAM

Full Credibility Standards

Limited fluctuation credibility determines how much weight to assign observed data versus prior expectations. Full credibility is achieved when the observed data is voluminous enough that the estimate meets a specified accuracy standard. The standard requires that the probability of the estimate being within k% of the true value exceeds a threshold p. For claim frequency, the full credibility standard is n0 = (z_p/k)^2, where z_p is the standard normal percentile. For aggregate losses, variance of severity adds an additional factor.

Partial Credibility

When data falls short of full credibility, the credibility factor Z = sqrt(n/n0) weights observed experience against the complement of credibility applied to a prior estimate. The credibility-weighted estimate is Z times the observed value plus (1-Z) times the prior. This approach balances responsiveness to actual experience with stability from prior knowledge. Exam STAM tests your ability to calculate n0 for different accuracy standards, compute Z for given data volumes, and apply credibility weighting to estimate future losses.