ECON 2300 Homework Assignment #6
Be sure to show your work for possible partial credit.
1.
A local kitchenware store periodically offers cooking classes at the back of the store. The manager is
curious about the amount of money attendees spend in the store as a result of the cooking classes. A
random sample of 64 cooking class attendees was surveyed over a 3month period. The mean amount
spent in the store per customer, as a result of attending a class, was $60 with a standard deviation of
$25.
a.
Determine and interpret a 90% confidence interval for the mean amount spent per customer, as a
result of attending a cooking class.
Standard Error =
x
σ
= 25/√64 = $3.13
Must use a critical tvalue because the population standard deviation,
σ
, is not known.
t
.05,63
=TINV(.10,63) = 1.67
Margin of Error = 1.67 * 3.13 = $5.23
90% confidence interval estimate = [$605.23; $60+5.23] = [54.77; 65.23]
Interpretation: It is estimated with 90% confidence that the average money spent per
customers attending a cooking class is between $54,77 and $65.23.
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 Spring '08
 DODONOVA
 Statistics, Normal Distribution, Standard Deviation, confidence interval estimate

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