Example problems for Chapter 9
1.
Acme claims that their oil changes take 50 minutes or less on average. If you take a
sample of size 100 and determine the sample mean is 52 minutes, can you disprove
ACMEs claim at the .05 level of significance? Assume the population standard deviation
is 10. Be sure to state the hypotheses and interpret your results in the context of the
problem. Use the critical z or t approach.
2.
Acme claims that their oil changes take 50 minutes or less on average. If you take a
sample of size 100 and determine the sample mean is 48 minutes, can you disprove
ACMEs claim at the .01 level of significance? Assume the population standard deviation
is 10. Be sure to state the hypotheses and interpret your results in the context of the
problem. Use the pvalue approach.
3.
A well known manufacturer of soda bottling equipment claims that the average fill rate of
the bottles they fill with the machine Coke purchased is 12 ounces. See if you can
disprove this. You have taken a sample of 64 bottles and found on average they contain
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 Spring '09
 Rollins
 Standard Deviation, 1 ounce, 48 minutes, 12 ounces, 11.9 ounces

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