Statistical process control: use of the c-chart The Y. B. Phatt Inc. produces a diet pow- der which is distributed worldwide. The powder is mixed with milk or water and comes in many flavors. The Y. B. Phatt powder has several ingredients some of which are vitamins and appetite suppressants. One of the appetite suppressants is homogenized cellulose which is processed from high quality sawdust. When mixed with a liquid the sawdust expands in volume and curbs people's appetite. The company purchases sawdust from local sawmills which are instructed not to exceed a normal percentage of white pine sawdust in the mixture of pine and hardwood sawdust the mills produce. Excess amounts of pine sawdust changes the absorbency of the diet powder which in the past has led to complaints from dissatisfied customers. Therefore, the company has decided that any batch that contains more than the stated amount of pine sawdust will be deemed unacceptable (defective). For the past 20 days the company has been sampling 100 batches each of delivered sawdust. The company found that out of 100 batches for each sample, the following were deemed unacceptable:

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Number of Unacceptable Number of Unacceptable Sample Batches Sample Batches 1 20 11 15 23450 12 4 5 6 10 7800 9 258302222 12 13 18 14 13 15 19 16 17 19 18 18 222 19 20 176284372 9