Critical Reasoning Example 1

1. Which of the following best completes the passage below?

In a survey of job applicants, two-fifths admitted to being at least a little dishonest. However, the survey may
underestimate the proportion of job applicants who are dishonest, because____.

A. some dishonest people taking the survey might have claimed on the survey to be honest
B. some generally honest people taking the survey might have claimed on the survey to be dishonest
C. some people who claimed on the survey to be at least a little dishonest may be very dishonest
D. some people who claimed on the survey to be dishonest may have been answering honestly
E. some people who are not job applicants are probably at least a little dishonest

2. The average life expectancy for the United States population as a whole is 73.9 years, but children born in
Hawaii will live an average of 77 years, and those born in Louisiana, 71.7 years. If a newlywed couple from
Louisiana were to begin their family in Hawaii, therefore, their children would be expected to live longer than
would be the case if the family remained in Louisiana.

Which of the following, if true, would most seriously weaken the conclusion drawn in the passage?

A. Insurance company statisticians do not believe that moving to Hawaii will significantly lengthen the average
Louisianan’s life.
B. The governor of Louisiana has falsely alleged that statistics for his state are inaccurate.
C. The longevity ascribed to Hawaii’s current population is attributable mostly to genetically determined factors.
D. Thirty percent of all Louisianans can expect to live longer than 77 years.
E. Most of the Hawaiian Islands have levels of air pollution well below the national average for the United
States.

Solutions:

1. A is the best answer.
If applicants who are in fact dishonest claimed to be honest, the survey results would show a smaller proportion of dishonest applicants than actually exists. Therefore, this choice is the best answer. B is inappropriate because generally honest applicants who claimed to be dishonest could contribute to the overestimation, but not to the underestimation, of dishonest applicants. D is inappropriate because applicants who admitted their dishonesty would not contribute to an underestimation of the proportion of dishonest applicants. C and E are inappropriate because the argument is concerned neither with degrees of dishonesty nor with the honesty of non-applicants.

2.C is the best answer.
This choice suggests that a significant proportion of Hawaii’s population is genetically predisposed to be long lived. Since Louisianans are not necessarily so predisposed, and since the Louisianans’ children will acquire their genetic characteristics from their parents, not from their birthplace, this choice presents a reason to doubt that Hawaiian born children of native Louisianans will have an increased life expectancy. Therefore, this choice is the best answer. Because the conclusion concerns people born in Hawaii, not the average Louisianan, A does not weaken the conclusion. Because the governor’s allegation is false, it cannot affect the conclusion. D fails to weaken the conclusion because it is consistent with the information given and the conclusion about life expectancy. By suggesting that Hawaii’s environment is in one respect particularly healthy, E supports the conclusion.