Product Discriminating Device, Product Discriminating Method, and Computer Program

A product discriminating method comprising the steps of:

• measuring characteristic values indicating predetermined characteristics of products;
• discriminating the products into a predetermined plurality of ranks based on the measured characteristic values;
• calculating a standard deviation of variation in the measured characteristic values as a deemed standard deviation;
• re-measuring characteristic values of the products belonging to at least one of the discriminated predetermined plurality of ranks and re-discriminating the products into the predetermined plurality of ranks based on the re-measured characteristic values;
• estimating the number of the products belonging to each of the ranks when re-discriminated at least once based on a probability distribution of the deemed standard deviation having a standard deviation of characteristic value variation of the products and a standard deviation of measurement value variation as variables, and calculating an estimated number of the products belonging to each of the ranks;
• and
• changing the variables of the probability distribution of the deemed standard deviation such that the number of the products belonging to at least one of the plurality of ranks re-discriminated at least once and the estimated number of the products belonging to the rank substantially match each other, and calculating the changed variables as the standard deviation of the characteristic value variation of the products and the standard deviation of the measurement value variation.

A non-transitory computer-readable medium executable in a product discriminating device for discriminating products;

• the computer-readable medium causing the product discriminating device to:
• measure characteristic values indicating predetermined characteristics of products;
• discriminate the products into a predetermined plurality of ranks based on the measured characteristic values;
• calculate a standard deviation of variation in the measured characteristic values as a deemed standard deviation;
• re-measure characteristic values of the products belonging to at least one of the discriminated predetermined plurality of ranks and re-discriminate the products into the predetermined plurality of ranks based on the re-measured characteristic values;
• estimate the number of the products belonging to each of the ranks when re-discriminated at least once based on a probability distribution of the deemed standard deviation having a standard deviation of characteristic value variation of the products and a standard deviation of measurement value variation as variables, and calculate an estimated number of the products belonging to each of the ranks;
• and
• change the variables of the probability distribution of the deemed standard deviation such that the number of the products belonging to at least one of the plurality of ranks re-discriminated at least once and the estimated number of the products belonging to the rank substantially match each other, and calculate the changed variables as the standard deviation of the characteristic value variation of the products and the standard deviation of the measurement value variation.