3. A pharmaceutical company wants to market what seems to be a revolutionary new drug: a near-cure for the common cold. Researchers in the R & D division randomly select 1,000 persons from the city where the company is headquartered to participate in a test study. Each participant is observed for six months. For the first three months, baseline data are collected. For the last three months, the participants take a weekly dose of the common-cold cure. Sure enough, 15 percent of the participants contracted a cold during the first three months, whereas only 2 percent did so in the second three months.
a. Using the notation introduced in Chapter 8, carefully diagram the design of this study. Be sure to label or specify the meaning of each "letter" in the diagram.
b. Is this a true experiment? If so, describe the design features that make it a true experiment. If not, describe what feature(s) of a true experiment are missing.
c. What is the purpose of randomly selecting participants? Does this enhance the internal validity or external validity of the study?
d. The investigators are confident that they have accurately recorded the incidence of colds and that the observed difference (15 percent versus 2 percent) is statistically significant. Therefore, they rush their findings to you, the company president, who must decide whether the data are convincing enough for the company to put the product on the market. Knowing about threats to internal validity, you consider the following: selection, statistical regression, history, instrumentation, and attrition. Which, if any, of these threats might undermine the validity of this study? Briefly explain.

Question

3. A pharmaceutical company wants to market what seems to be a revolutionary new drug: a near-cure for the common cold. Researchers in the R & D division randomly select 1,000 persons from the city where the company is headquartered to participate in a test study. Each participant is observed for six months. For the first three months, baseline data are collected. For the last three months, the participants take a weekly dose of the common-cold cure. Sure enough, 15 percent of the participants contracted a cold during the first three months, whereas only 2 percent did so in the second three months.
a. Using the notation introduced in Chapter 8, carefully diagram the design of this study. Be sure to label or specify the meaning of each "letter" in the diagram.
b. Is this a true experiment? If so, describe the design features that make it a true experiment. If not, describe what feature(s) of a true experiment are missing.
c. What is the purpose of randomly selecting participants? Does this enhance the internal validity or external validity of the study? 
d. The investigators are confident that they have accurately recorded the incidence of colds and that the observed difference (15 percent versus 2 percent) is statistically significant. Therefore, they rush their findings to you, the company president, who must decide whether the data are convincing enough for the company to put the product on the market. Knowing about threats to internal validity, you consider the following: selection, statistical regression, history, instrumentation, and attrition. Which, if any, of these threats might undermine the validity of this study? Briefly explain.

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The Answer of 3. A pharmaceutical company wants to market what seems to be a revolutionary new drug: a near-cure for the common cold. Researchers in the R & D division randomly select 1,000 persons from the city where the company is headquartered to participate in a test study. Each participant is observed for six months. For the first three months, baseline data are collected. For the last three months, the participants take a weekly dose of the common-cold cure. Sure enough, 15 percent of the participants contracted a cold during the first three months, whereas only 2 percent did so in the second three months.
a. Using the notation introduced in Chapter 8, carefully diagram the design of this study. Be sure to label or specify the meaning of each "letter" in the diagram.
b. Is this a true experiment? If so, describe the design features that make it a true experiment. If not, describe what feature(s) of a true experiment are missing.
c. What is the purpose of randomly selecting participants? Does this enhance the internal validity or external validity of the study? 
d. The investigators are confident that they have accurately recorded the incidence of colds and that the observed difference (15 percent versus 2 percent) is statistically significant. Therefore, they rush their findings to you, the company president, who must decide whether the data are convincing enough for the company to put the product on the market. Knowing about threats to internal validity, you consider the following: selection, statistical regression, history, instrumentation, and attrition. Which, if any, of these threats might undermine the validity of this study? Briefly explain.

3 a Pharmaceutical Company Wants to Market What Seems to Be