A researcher determined the size sample necessary to estimate two population means Y and Z. The indicated sizes were 200 to estimate Y and 300 to estimate Z with the specified degrees of confidence and precision. The researcher decided therefore to use a sample of size 250 . Assuming the estimates of the population standard deviation were correct
a. the estimate of Y is more precise than desired while that for Z is less precise than desired.
b. the estimate of Y is less precise than desired while that for Z is more precise than desired.
c. Y is estimated with exactly the specified degree of precision while Z is estimated less precisely than desired.
d. Z is estimated with exactly the specified degree of precision while Y is estimated less precisely than desired.
e. Both Y and Z are estimated with the exact specified degree of precision.
Question 2If the sample standard deviation turns out to be larger than the estimated population standard deviation, the confidence interval to estimate a population mean will be __________ planned.
a. Narrower than
b. Wider than
c. The same as
d. As precise as
e. None of the above
Question 3A researcher estimated an unknown population standard deviation to be 150 . Using a sample of size n = 135, the sample standard deviation was found to be 100 . The researcher now wishes to establish a 95 confidence interval for the population mean. Which of the following is the correct standard error of the mean to use in calculating the desired confidence interval?
a. Can't be determined from the information given.
b. 1.05
c. 12.91
d. 0.86
e. 8.61
Question 4In the above problem, if the desired precision is +25 and the desired confidence interval is 95, what is the necessary sample size?
a. 240
b. 540
c. 92
d. 64
e. None of the above.
Question 5A researcher is attempting to determine the average annual expenditures per household on compact discs. Suppose 600 was considered the upper limit and 0 the lower limit. There are no past studies on which to base an estimate of . What is your best estimate of the standard deviation?
a. 120
b. 200
c. 100
d. 300
e. No way to determine.
Question 6If the estimated range of incomes for 30 medium size businesses is 60,000, a rough estimate of one standard deviation would be
a. 10,000.
b. 12,000.
c. 8,000.
d. 8,500.
e. 9,000.
Question 7A researcher is attempting to determine the average annual expenditures per household on albums. Suppose 300 was considered the upper limit and 0 the lower limit. There are no past studies on which to base an estimate of . What is your best estimate of the standard deviation?
a. 0
b. 50
c. 150
d. 300
e. No way to determine.
Question 8Suppose that the income of the population of the city of Seattle is normally distributed and varies approximately from 0 to 6 million; what is the estimated standard deviation?
a. Insufficient information to estimate
b. 2 million
c. 3 million
d. square root of 6 million
e. 1 million
Question 9Which of the following is NOT an acceptable method of estimating the population standard deviation?
a. Perform a pilot study.
b. Divide the estimated range of variation by 2.
c. Use an estimate based on past studies of the same phenomenon.
d. Divide the estimated range of variation by 6.
e. Use an estimate based on the method used to measure the important variables.
Question 10Toppen Olaf Olson, plant manager at the Ridgway Tanning Factory, was interested in the average number of hides currently sold each day at the plant. The daily variance of hides sold at the plant last year was 132 . Olaf would like to be 90 percent confident (z = 1.645) in his results and be within a daily range of +/ 5 hides. Olaf needs a sample of what size to achieve his desired level of precision and confidence?
a. 15
b. 22
c. 472
d. 1,886
e. 2,788
Question 11Referring again to Stella's situation in Question 15, if Stella wishes to increase the total precision to 5, how many observations are needed?
a. 8
b. 54
c. 48
d. 96
e. 24
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