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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 8hour
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 cerealfilling 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.
 Spring '13

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