Joshua concludes that it is a cause for alarm that majority of the people surveyed knows someone who has been a victim of crime. It is also inferred that a few people said in the survey that they don't know anyone who has been a victim of crime.

Laura provides evidence that it is unrealistic for someone to not know even one person who has been a victim crime. Thereby, affirming the conclusion from the survey.

The only way this conclusion can hold true is if the survey was given to a representative sample of the population. So IMO ans. E is correct

Laura: But each person surveyed probably knows a hundred people. If only one person out of one hundred acquaintances had been a victim of a crime, even a pretty theft, they would reply in the affirmative. Although a zero crime rate is ideal, it is unrealistic to expect the crime rate to be less than one percent.

each person probably know hundred people - the author is assuming that : the ratio of one person out of one hundred is a victim of crime - in spite of the fact that the distribution may vary from demographic zone or some other factors.
It may be possible that 1% distribution is not equal in all areas - it may vary ( consider weighted average) !!

Laura's conclusion is based on this following assumption - unrealistic to expect the crime rate to be less than 1%.

may be possible that - in some areas it is 0.5% and in some it is 1.5%.

So E is the exact point of this assumption.

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Try negation :
A. the crime rate rarelyalways goes above one percent. --- an assumption is not something that weakens the premise/facts.

B. Joshua is not accurately reporting the statistics he presents. --- laura's point is based on the fact that Joshua is accurately reporting.

C. the number of people who know someone who is a victim of crime is always higher than fifty percent of the population. --- same error like A.

D. awareness of a crime committed against an acquaintance generates more fear than does knowledge of crime statistics. --- deals with an irrelevant topic : awareness

E. normally, crime victims are not found only in certain areas of the state among certain isolated groups of people.--- some areas 0.5% and in some areas more than 1% : so its possible to expect less than one percent ( weighted average = 1%)

Avik.ch Thank you for your explanation. Now I got it. My problem was I couldn't pay attention to the stimulus in details within 2 mins. I misunderstood "one person out of one hundred acquaintances had been a victim of a crime" for "one person out of one hundred acquaintances had known a victim of a crime". That's why I got confused..

When statistics or survey results are mentioned in CR, you should immediately check to make sure that the evidence supports the conclusion, or what assumptions are needed for it to do so. I will go so far as to say that CR with surveys/data that do NOT test this are rare.