67.       
　　The president of the company that produces Glabrous Shampoo argues against removing the ingredient HR2 from the shampoo even though a scientific study claims that prolonged use of HR2 can contribute to hair loss. Three reasons are cited as the basis for this decision. First, it is argued that since the scientific study involved only 500 subjects, it can be disregarded. Second, none of Glabrous' customers have complained of problems during the past year. And, finally, Glabrous' competitors use more HR2 per bottle than Glabrous. The president's decision is problematic in several respects.

      To begin with, the fact that the scientific study on HR2 involved only 500 subjects is insufficient¹ grounds to dismiss the results of that study. If the subjects for the study were randomly² chosen and represent a diverse cross section of the population of shampoo users, the results will be reliable regardless of the number of participants.

      Next, the scientific study determined³ that prolonged use could contribute to hair loss. While "prolonged use" was not defined in the memorandum⁴, the fact that none of Glabrous' customers have complained of problems during the past year is not a reliable reason to believe that problems will not arise in the future.

      Finally, the fact that Glabrous' competitors use more HR2 in their products than Glabrous uses is irrelevant⁵ to the question of whether Glabrous should remove HR2 from its product. Moreover, rather than providing a reason for not removing the compound, this fact serves better as a reason for doing so. By removing HR2 from its product Glabrous could gain an edge over its competitors.

      In conclusion, the reasoning in this argument is not convincing. To strengthen the argument the author would have to show that the study was biased⁶ or was based on too small a sample to yield reliable results.
68.      
　　 The author of this editorial concludes that the guidelines for training pilots and maintaining equipment in the medical-helicopter industry are ineffective, even though they are far more stringent⁷ than those in other airline industries. To support this conclusion, the author cites statistics showing that the rate of medical-helicopter accidents is much higher than the rate of accidents for non-medical helicopters or commercial airliners⁸. This argument is problematic in three critical respects.

      The first problem with the argument is that it rests on the unstated assumption that accidents involving medical helicopters have been due to inadequate⁹ pilot training or equipment maintenance. However, the author fails to acknowledge and rule out other possible causes of such accidents. In fact, common sense tells us that medical-helicopter accidents are most likely to result from the exigent circumstances and dangerous flying and landing conditions which typifymedical emergencies where helicopters are required to gain access to victims.

      A second, and related, problem is that the author unfairly compares the accident rate of medical helicopters with the accident rate for non-emergency aircraft. Medical helicopters are almost invariably deployed¹⁰ during emergencies to dangerous flying locales, whereas other types of aircraft are not. Consequently. medical-helicopter accidents will in all likelihood occur far more frequently than other aircraft accidents, regardless of pilot training or equipment maintenance.

      A third problem with the argument is that the statistical¹¹ evidence upon which it relies is too vague to be informative¹². The statistics concerning aircraft accidents may have been based on all types of accidents, whether minor¹³ or major. The statistics would be more meaningful if we knew that the accidents to which they refer were all of comparable severity. For all we know, the rate of casualty-causing accidents for medical helicopters is actually lower than for other aircraft. Additionally, we are not told the time period of the survey. An old survey or one that covered only a brief time period would be poor evidence in support of the author's claim.

      In conclusion, the author's evidence does little to support the conclusion. To be persuasive¹⁴, the author must at the very least acknowledge and rule out other possible causes of accidents that are unique to the medical-helicopter industry, in any event, a more effective argument would be based on a statistical comparison of accident rates under differing sets of training and maintenance guidelines within :he medical-helicopter industry, not among different aircraft industries.