SOLUTION: A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall. Fifteen cr

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Question 314551: A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: sample mean = $50.50 and sample variance = $400. Assuming the distribution of the amount spent on their first visit is approximately normal, what is the shape of the sampling distribution of the sample mean that will be used to create the desired confidence interval for u?
a. approximately normal with a mean of $50.50
b. a standard normal distribution.
c. a "t" distribution with 15 degrees of freedom.
d. a "t" distribution with 14 degrees of freedom.

If an economist wishes to determine whether there is evidence that average family income in a community equals $25,000:
a. either a one-tailed or two tailed test could be used with equivalent results.
b. a one-tailed test should be utilized.
c. a two-tailed test should be utilized.
d. none of the above.
An appliance manufacturer claims to have developed a compact microwave oven that consumes an average of no more than 250W. From previous studies, it is believed that power consumption for microwave ovens is normally distributed with a standard deviation of 15W. A consumer group has decided to try to discover if the claim appears true. They take a sample of 20 microwave ovens and find that they consume an average of 257.3 W. The population of interest is:
a. the power consumption in the 20 microwave ovens.
b. the power consumption in all such microwave ovens.
c. the mean power consumption in the 20 microwave ovens.
d. the mean power consumption in all such microwave ovens.
Given the problem above, the appropriate hypothesis to determine if the manufacturer's claim appears reasonable is:
a. Ho : u = 250 versus H1 : u =/ 250
b. Ho : u >= 250 versus H1 : u < 250
c. Ho : u <= 250 versus H1 : u > 250
d. Ho : u >= 257.3 versus H1 : u < 257.3
A drug company is considering marketing a new local anesthetic. The effective time of the anesthetic the drug company is currently producing has a normal distribution with an average of 7.4 minutes with a standard deviation of 1.2 minutes. The chemistry of the new anesthetic is such that the effective time should be normal with the same standard deviation, but the mean effective time may be lower. If it is lower, the drug company will market the new anesthetic; otherwise they will continue to produce the older one. A sample size of 36 results in a sample mean of 7.1. A hypothesis test will be done to help make the decision. The appropriate hypotheses are:
a. Ho : u = 7.4 versus H1 : u =/7.4
b. Ho : u <= 7.4 versus H1 : u > 7.4
c. Ho : u >= 7.4 versus H1 : u < 7.4
d. Ho : u > 7.4 versus H1 : u <= 7.4
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Answer by jack_barbosa(1) About Me  (Show Source):
You can put this solution on YOUR website!
c. Ho : u <= 250 versus H1 : u > 250