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Chapter 1: Q9. (page 49)
What is a representative sample? What is its value?
The representative sample is the group that provides information on the entire population and is of great value for researchers and statisticians.
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Monitoring the production of soft-drink cans. The Wakefield plant of Coca-Cola and Schweppes Beverages Limited (CCSB) can produce 4,000 cans of soft drink per minute. The automated process consists of measuring and dispensing the raw ingredients into storage vessels to create the syrup and then injecting the syrup, along with carbon dioxide, into the beverage cans. In order to monitor the sub process that adds carbon dioxide to the cans, five filled cans are pulled off the line every 15 minutes, and the amount of carbon dioxide in each of these five cans is measured to determine whether the amounts are within prescribed limits.
a. Describe the process studied.
b. Describe the variable of interest.
c. Describe the sample.
d. Describe the inference of interest.
e. Brix is a unit for measuring sugar concentration. If a technician is assigned the task of estimating the average brix level of all 240,000 cans of beverage stored in a warehouse near Wakefield, will the technician be examining a process or a population? Explain.
Jamming attacks on wireless networks. Terrorists often use wireless networks to communicate. To disrupt these communications, the U.S. military uses jamming attacks on the wireless networks. The International Journal of Production Economics (Vol. 172, 2016) described a study of 80 such jamming attacks. The configuration of the wireless network attacked was determined in each case. Configuration consists of network type (WLAN, WSN, or AHN) and number of channels (single- or multi-channel).
a. Suppose the 80 jamming attacks represent all jamming attacks by the U.S. military over the past several years, and these attacks are the only attacks of interest to the researchers. Do the data associated with these 80 attacks represent a population or a sample? Explain.
b. The 80 jamming attacks actually represent a sample. Describe the population for which this sample is representative.
c. Identify the variable 鈥渘etwork type鈥� as quantitative or qualitative.
d. Identify the variable 鈥渘umber of channels鈥� as quantitative or qualitative.
e. Explain how to measure number of channels quantitatively?
Explain the difference between descriptive and inferential statistics.
List the three major methods of collecting data and explain their differences.
The economic return to earning an MBA. What are the economic rewards (e.g., higher salary) to obtaining an MBA degree? This was the question of interest in an article published in the International Economic Review (August 2008). The researchers made inferences based on wage data collected for a sample of 3,244 individuals who sat for the Graduate Management Admissions Test (GMAT). (The GMAT exam is required for entrance into most MBA programs.) The following sampling scheme was employed. All those who took the GMAT exam in any of four selected time periods were mailed a questionnaire. Those who responded to the questionnaire were then sent three follow-up surveys (one survey every 3 months). The final sample of 3,244 represents only those individuals who responded to all four surveys. (For example, about 5,600 took the GMAT in one time period; of these, only about 800 responded to all four surveys.)
A. For this study, describe the population of interest.
b. What method was used to collect the sample data?
c. Do you think the final sample is representative of the population? Why or why not? Comment on potential biases in the sample.
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