2. Difference estimation method: a variable sampling method to infer the difference between the overall record value and the audit value through the difference between the sample record value and the audit value, and then evaluate the overall record value.
3. Ratio estimation method: a variable sampling method to infer the ratio of the overall audit value to the recorded value through the ratio of the audit value to the sample recorded value, and then estimate the overall audit value and evaluate the correctness of the original recorded value.