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Subject: Economics    / General Economics
Question
QUESTION 1

In a sample of 100 people who have had strokes, the average cholesterol level was 250 with a standard deviation of 40. In order to test the hypothesis (at the 5% level of significance) that the average cholesterol level of people who have had strokes was at least 240, what is the null and alternative hypotheses?

5 points

QUESTION 2

The amount of gas a local gas station sells is random. The following describes the distribution of gasoline sales in a given day. There is a probability of 0.11 that the station will sell 1100 gallons of gas; there is a probability of 0.28 that the station will sell 1300 gallons of gas; there is a probability of 0.34 that the station will sell 1600 gallons of gas; otherwise, the station sells 2000 gallons of gas. What is the expected number of gallons the station sells in a day? (please express your answer using 2 decimal places)

15 points

QUESTION 3

Over the past 50 years, the number of hurricanes that have been reported are as follows: 9 times there were 6 hurricanes, 14 times there were 8 hurricanes, 19 times there were 10 hurricanes, and in the remaining years there were 14 hurricanes. What is the mean number of hurricanes is a year? (please round your answer to 1 decimal place)

15 points

QUESTION 4

Historically, the proportion of students entering a university who finished in 4 years or less was 64%. To test whether this proportion has decreased, 129 students were examined and 49% had finished in 4 years or less. To determine whether the proportion of students who finish in 4 year or less has statistically significantly decreased (at the 10% level of signficance), what is the critical value? (please round your answer to 2 decimal places)

5 points

QUESTION 5

Suppose that a particular large hotel has 790 rooms. Furthermore, suppose that for weekend nights the mean demand for rooms is 730 rooms with a standard deviation of 35 rooms. What is the probability that over a sample of 35 weekend nights, the hotel will sell at least an average of 740 rooms over this sample? (please round your answer to 4 decimal places)

10 points

QUESTION 6

A grocery store manager would like to have an idea concerning the average amount milk the store sells per day. In a sample of 57 days, the average amount number of gallons sold was 115 with a standard deviation of 24 gallons. What is theupper bound of the 95% confidence interval? (please express your answer using 2 decimal places)

5 points

QUESTION 7

In an effort to reduce energy costs, a major university has installed more efficient lights as well as automatic sensors that turn the lights off when no movement is present in a room. Historically, the cost of lighting an average classroom for 1 week has been \$265. To determine whether the changes have signficantly reduced costs, the university takes a sample of 50 classrooms. They find that the average cost for 1 week is \$247 with a standard deviation of \$60. When testing the hypothesis (at the 5% level of significance) that the average energy use has decreased from the past, what is the p-value? (please round your answer to 4 decimal places)

5 points

QUESTION 8

Historically, the proportion of students entering a university who finished in 4 years or less was 63%. To test whether this proportion has decreased, 120 students were examined and 52% had finished in 4 years or less. To determine whether the proportion of students who finish in 4 year or less has statistically significantly decreased (at the 5% level of signficance), what is the p-value? (please round your answer to 4 decimal places). The p-value for the test of whether the proportion of students who finish in 4 years or less has decreased is 0.0207. If we were to test this hypothesis at the 5% level of signficance, what can you conclude concerning the null hypothesis?
Reject the null hypothesis
Fail to reject the null hypothesis

5 points

QUESTION 9

What is the t-value associated with 22 degrees of freedom and 5% in the tail? (please round your answer to 3 decimal places)

10 points

QUESTION 10

In the past, the value of houses a local realtor has sold is normally distributed with a mean of \$195,000 with a standard deviation of \$28,000. What is the probability that the next house the realtor sells has a value over \$160,000? (please round your answer to 4 decimal places)

10 points

QUESTION 11

Suppose the following data show the introductory interest rates on a sample of 5 credit cards: 5.7, 2.8, 3, 4.2, 3.9. Calculate the mean interest rate of the sample. (please express your answer using 2 decimal places)

15 points

QUESTION 12

In an effort to reduce energy costs, a major university has installed more efficient lights as well as automatic sensors that turn the lights off when no movement is present in a room. Historically, the cost of lighting an average classroom for 1 week has been \$265. To determine whether the changes have signficantly reduced costs, the university takes a sample of 84 classrooms. They find that the average cost for 1 week is \$244 with a standard deviation of \$63. When testing the hypothesis (at the 5% level of significance) that the average energy use has decreased from the past, what is the test statistic? (please round your answer to 2 decimal places)

5 points

QUESTION 13

Suppose the country club bills based on a sample of 4 members are: 383, 1,051, 637, 928. What is the standard deviation for this sample of bills? (please round your answer to 1 decimal place)

15 points

QUESTION 14

In the past, the value of houses a local realtor has sold is normally distributed with a mean of \$232,000 with a standard deviation of \$61,000. How much does a house have to sell for so that the house is in the bottome 5% of lowest selling houses for the realtor? (please express your answer in \$'s)