1. A sampling inspection estimating method comprising: determining an acceptable range of a measured value and an acceptable range of a acceptance probability; determining a first sampling plan to be inspected and a condition of calculating a first acceptance variables of lots; obtaining a first measured value of a production lot based on the determined first sampling plan; calculating first acceptance variables of lots based on the obtained first measured value and the determined condition of calculating the first acceptance variables of lots; calculating a first acceptance probability based on the first acceptance variables of lots; determining a second sampling plan to be inspected and a condition of calculating a second acceptance variables of lots; obtaining a second measured value of a production lot based on the determined second sampling plan; calculating second acceptance variables of lots based on the obtained second measured value and the determined condition of calculating the second acceptance variables of lots; calculating a second acceptance probability based on the second acceptance variables of lots; calculating operating characteristics of the first and second sampling plans based on the first acceptance probability and the second acceptance probability; and estimating the operating characteristics by using the determined acceptable range of the acceptance probability.