8.1 Estimation Using Normal

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Unformatted text preview: to determine the population mean —use a sample to make inference about population mean. σ Known Example Oxford Cereals fills thousands of boxes of cereal during an 8-hour shift. The be consistent with package labeling, boxes should contain a mean of 368 grams of cereal. Because of the speed of the process, the cereal weight varies from box to box, causing some boxes to be underfilled and others overfilled (the standard deviation is known to be 0.15 grams). If the process is not working properly, the mean weight in the boxes could vary too much from the label weight of 368 grams to be acceptable. Interval Estimation Because weighing every box is too costly, a sample of boxes is selected. The sample is used to decide whether to maintain, alter, or shut down the cereal-filling process. No way to determine the population mean —use a sample to make inference about population mean. Based on the sample, how will they determine whether or not the process is working? σ Known Example Based on the sample, how will they determine whether or not the process is working? Interval Estimation σ Known Example Based on the sample, how will they determine whether or not the process is working? Recall sampling error, the difference between the sample mean and the population mean ◦ Is the sampling error an acceptable amount, or is the difference too large? E.g., if sample mean is 342.3 gm, does it seem possible that population mean is 368 gm? maybe not E.g., if sample mean is 365.8 gm, does it seem possible that the population mean is 368 gm? probably Interval Estimation σ Known Example Based on the sample, how will they determine whether or not the process is working? Recall sampling error, the difference between the sample mean and the population mean ◦ Is the sampling error an acceptable amount, or is the difference too large? Interval Estimation Ø E.g., if sample mean is 342.3 gm, does it seem possible that population mean is 368 gm? maybe not E.g., if sample mean is 365.8 gm, does...
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This document was uploaded on 03/05/2014.

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