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ECN 221- Exam 3 Questions with Answers.
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Practice Questions Exam 3MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) A ________ for the mean is an interval estimate around a sample mean that provides us with a 1)
range of where the true population mean lies.
A) confidence interval B) confidence level
C) margin of error D) significance level
2) When calculating a confidence interval for the mean using a sample size of 30 or more with a 2)
known population standard deviation, the ________ is used.
A) binomial distribution B) Student's t-distribution
C) Poisson distribution D) normal distribution
3) A random sample of 30 business students required an average of 43.4 minutes to complete a 3)
statistics exam. Assume that the population standard deviation to complete the exam was 8.7
minutes. The 95% confidence interval around this sample mean is ________.
A) (40.3, 46.5) B) (41.4, 45.4) C) (40.8, 46.0) D) (42.0, 44.8)
4) A random sample of 30 business students required an average of 43.4 minutes to complete a 4)
statistics exam. Assume that the population standard deviation to complete the exam was 8.7
minutes. The margin of error for a 98% confidence interval around this sample mean is ________.
A) 3.70 B) 2.04 C) 3.12 D) 2.62
5) A ________ represents the width of the confidence interval between a sample mean and its upper 5)
limit or between a sample mean and its lower limit.
A) significance level B) confidence interval
C) margin of error D) confidence level
6) A survey by American Express Spending reported that the average amount spent on a wedding 6)
gift for a close family member is $166. A random sample of 45 people who purchased wedding
gifts for a close family member spent an average of $160.50. Assume that the population standard
deviation is $38. Use a 95% confidence interval to test the validity of this report and choose the one
statement that is correct.
A) Because this confidence interval does include $166, the report by American Express Spending
is not validated.
B) Because this confidence interval does include $166, the report by American Express Spending
is validated.
C) Because this confidence interval does not include $166, the report by American Express
Spending is not validated.
D) Because this confidence interval does not include $166, the report by American Express
Spending is validated.
7) When calculating a confidence interval for the mean using a sample size of less than 30 with an 7)
unknown population standard deviation, the ________ is used.
A) Poisson distribution B) normal distribution
C) binomial distribution D) Student's t-distribution
1
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, 8) A random sample of 20 roundtrip flights between Philadelphia and Dallas has an average airfare of 8)
$470.40 with a sample standard deviation of $58.70. The 95% confidence interval around this
sample mean is ________.
A) ($442.92, $497.88) B) ($457.27, $483.53)
C) ($431.01, $509.79) D) ($417.88, $522.92)
9) A random sample of 130 mortgages in the state of Mississippi was randomly selected. From this 9)
sample, 14 were found to be delinquent on their current payment. The 90% confidence interval for
the proportion based on this sample is ________.
A) (0.063, 0.153) B) (0.015, 0.201) C) (0.029, 0.188) D) (0.036, 0.180)
10) The National Center for Education would like to estimate the average student debt for the class of 10)
2010 for the state of Ohio with a 95% confidence interval and a margin of error within plus or
minus $2,000. Assuming the standard deviation for student debt in this state is $9,000, the required
sample size is ________.
A) 62 B) 78 C) 95 D) 40
11) If the purpose of the hypothesis test is to establish that a population parameter is equal to or not 11)
equal to a specific value, the
A) equality statement is always assigned to the alternative hypothesis.
B) or statement is always assigned to the alternative hypothesis.
C) equality statement is always assigned to the null hypothesis.
D) statement is always assigned to the null hypothesis.
12) A professor would like to test the hypothesis that the average number of minutes that a student 12)
needs to complete a statistics exam is equal to 45 minutes. A Type I error would occur if the
professor concludes that the average exam time is
A) equal to 45 minutes when, in reality, the average time is less than 45 minutes.
B) not equal to 45 minutes when, in reality, the average time is equal to 45 minutes.
C) not equal to 45 minutes when, in reality, the average time is greater than 45 minutes.
D) equal to 45 minutes when, in reality, the average time is not equal to 45 minutes.
13) The p-value for a hypothesis test is defined as the probability of observing a 13)
A) critical value at least as extreme as the one selected for the hypothesis test, assuming the null
hypothesis is true.
B) critical value at least as extreme as the one selected for the hypothesis test, assuming the null
hypothesis is false.
C) population mean at least as extreme as the one selected for the hypothesis test, assuming the
alternative hypothesis is true.
D) sample mean at least as extreme as the one selected for the hypothesis test, assuming the null
hypothesis is true.
2
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