Situation For one manufacturing process, the product is made in batches. After each batch is completed, it is tested. If the batch does not meet specifications for percent solids, it is reworked. This test and rework cycle continues until the batch either meets specification or it is scrapped. The batches that meet specifications are shipped to the customer. Some of the scrapped batches are kept to use in the rework of future batches, while others are thrown out. Available data Each time a batch of product is tested, the test results are entered into a database. Therefore, all test values are stored. Data from the past 20 batches of product are given in the table below. Batch number, revision number, and the value for percent solids are given. If the batch passed with no rework required, the revision number is 1. If one rework cycle was required, the batch revision number is 2 and so on for additional revisions until the value is in specification. Specifications for percent solids for this product are 55 ± .5 Questions 1. How can you use these data values to show the customer that you are meeting specifications? 2. How can you use these data values to understand the production process? 3. Of what use are Cp and Cpk for this process?
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