QUESTION 3

1. The sampling error is the:

   		Same as the standard error of the mean
   		Error caused by selecting a bad sample
   		Standard deviation multiplied by the sample size
   		Difference between the value of the sample mean and the value of the population mean
   		None of the above

7.143 points

QUESTION 4

1. Which of the following is the amount that is added to or subtracted from the sample mean to construct an interval estimate of the population mean?

   		Level of significance
   		Margin of error
   		Standard error
   		z score
   		Confidence coefficient

7.143 points

QUESTION 5

1. Which of the following is a factor that influences interval width?

   		confidence level
   		Sample size n
   		Variation in the population as measured by its standard deviation
   		All of the above
   		None of the above

7.143 points

QUESTION 6

1. When constructing a confidence interval, an increase in sample size will:

   		Increase the margin of error and increase the standard error
   		Increase the margin of error and increase the standard error
   		Decrease both the margin of error and the standard error
   		Increase both the margin of error and the standard error
   		Will have no effect on the confidence interval

7.143 points

QUESTION 7

1. You want to estimate the average GMAT score for all students who took the Logitano GMAT Preparation course during the past 2 years. You select a random sample of 100 such students from a comprehensive list of all students who took the course over the last two years and find that the average GMAT score for the sample was 1040. Suppose now you build a 95% confidence interval estimate of the average score for the population of Logitano students represented here and the interval turns out to be 1040 10 points. How would you interpret your result?

   		We can be 95% confident that the interval 1030 to 1050 contains the average score for the entire population of Logitano students.
   		The score for 95% of all Logitano students will be between 1030 and 1050.
   		There is a 5% chance that not all Logitano students scored between 1030 and 1050.
   		We can be 95% confident that all of Logitano students scored between 1030 and 1050.
   		Ninety-five percent of the scores for all Logitano students will be between 1030 and 1050.

7.143 points

QUESTION 8

1. From a population that is normally distributed with an unknown standard deviation, a sample of 25 elements is selected. For an interval estimation of the population mean, the proper distribution to use is the:

   		t distribution with 24 degrees of freedom
   		t distribution with 26 degrees of freedom
   		standard normal distribution
   		normal distribution
   		none of the above

7.143 points

QUESTION 9

1. In the sampling distribution of the sample mean, approximately 95.5% of the sample means will be within_______ standard error(s) of the population mean.

   		1.00
   		1.96
   		2.00
   		2.58
   		3.00

7.143 points

QUESTION 10

1. Which of the following factors would be used to determine sample size?

   		confidence level
   		the required precision (margin of error)
   		the degree of variation in the population as measured by its standard deviation
   		all of the above
   		none of the above

7.143 points

QUESTION 11

1. The Census Bureau of the US Department of Commerce estimated that average e-commerce sales for US retailers in the second quarter of 2011 had increased by 4.0 percent from the first quarter of 2011. Along with the estimate, a margin of error of 1.6 percent (at the 95% confidence level) was reported. Please show the upper and lower bounds for the 95% confidence level.

   		2.4% - 5.6%
   		4.0% - 5.6%
   		2.4% - 4.0%
   		2.0% - 6.0%
   		cannot be determined

7.143 points

QUESTION 12

1. TradeLine, is an online stock-trading service. To estimate the average number of trades made last month by TradeLines clients, you take a simple random sample of 16 clients and find the average number of trades in the sample is 45.8. Since you do not know the population standard deviation, you calculate the sample standard deviation as 12.3. Assume that the population is normally distributed. Show the appropriate 99% confidence interval for the average number of trades for all of TradeLines clients.

   		45.8 - 54.86
   		36.74 - 54.86
   		36.74 - 54.86
   		33.8 - 55.8
   		cannot be determined

7.143 points

QUESTION 13

1. The Lundberg Survey monitors gas prices at gas stations nationwide. In a recent month, Lundberg reported that the average regular gas price for the stations it surveyed was $3.40 per gallon. Assume the population distribution of gas prices is normal. The sample size was 24 stations. Because the population standard deviation is unknown, the researchers calculated a sample standard deviation of $.14. Please build a 90% confidence interval estimate of the average price of a gallon of gas for the population of gas stations nationwide. Please round your final answer to the nearest penny.

   		3.45 - 3.50
   		3.30 - 3.45
   		3.30 - 3.50
   		3.35 - 3.45
   		cannot be determined

7.143 points

QUESTION 14

1. A government auditor investigating consumer complaints about Gelman Merchandising over-charging its customers plans to select a simple random sample of Gelman customers to estimate the average overcharge amount per customer. The auditor plans to produce a 99% confidence interval estimate that is no wider than $25. For a pilot sample, the standard deviation of overcharge amounts is $330. Recommend the appropriate number of customers that need to be contacted for the investigation.

   		34
   		1258
   		116
   		697
   		1160