Math

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According to CTIA-The Wireless Association, the mean monthly cell phone bill in 2004 was \$50.64. A market
researcher believes that the mean monthly cell phone bill is different today, but is not sure whether bills have
declined because of technological advances or increased due to additional use. The researcher phones a simple
random sample of 12 cell phone subscribers and obtains the monthly bills
94.25 38.94 79.15 56.78
70.07 115.59 77.56 37.01
55.00 76.05 27.29 52.48
Assuming SD=\$18.49 and normal curve shape for the 2004 distribution of bills price, use the sample data to
determine whether the mean monthly cell phone bills is different from \$50.64 at the p=0.05 level of
significance.

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