Question

In a 1994 Senate subcommittee hearing, an executive of a major tobacco company testified that the accusation that nicotine was added to cigarettes was false. Tobacco company scientists stated that the amount of nicotine in cigarettes was completely determined by the size of the tobacco leaf, with smaller leaves having greater nicotine content. Thus, the variation in nicotine content in cigarettes occurred due to a variation in the size of the tobacco leaves and was not due to any additives placed in the cigarettes by the company. Furthermore, the company argued that the size of the leaves varied depending on the weather conditions during the growing season, over which they had no control. To study whether smaller tobacco leaves had a higher nicotine content, a consumer health organization conducted the following experiment. The major factors controlling leaf size are the temperature and the amount of water received by the plants during the growing ­season. The experimenters created four types of growing conditions for tobacco plants. Condition A was average temperature and rainfall amounts. Condition B was lower than average ­temperature and rainfall conditions. Condition C was higher than average temperature with lower than average rainfall. ­Finally, condition D was higher than average temperature and rainfall. The scientists then planted 10 tobacco plants under each of the four conditions in a greenhouse where temperature and amount of moisture were carefully controlled. After growing the plants, the scientists recorded the leaf size and nicotine content, which are given here:
a. Perform a one-way analysis of variance to test whether there is a significant difference in the average leaf sizes under the four growing conditions. Use α = .05.
b. What conclusions can you reach concerning the effect of growing conditions on the average leaf size?
c. Perform a one-way analysis of variance to test whether there is a significant difference in the average nicotine contents under the four growing conditions. Use α = .05.
d. What conclusions can you reach concerning the effect of growing conditions on the average nicotine content?
e. Based on the conclusions you reached in parts (b) and (d), do you think the testimony of the tobacco companies’ scientists is supported by this experiment? Justify your conclusions.


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  • CreatedNovember 21, 2015
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