Support All Labrador retrievers bark a great deal. Support All Saint Bernards bark infrequently. Support Each of Rosa's dogs is a cross between a Labrador retriever and a Saint Bernard. Therefore, Conclusion Rosa's dogs are moderate barkers.
This argument rests on the idea that parents with differing traits combine to produce an average of their traits in their offspring. Labrador retrievers bark a lot, and Sant Bernards don’t bark much, so their offspring must be moderate barkers.
This is a variation of the cookie-cutter part vs. whole flaw: the author assumes that combining two parts together forms a whole whose traits must sit squarely between the original parts. But that’s not necessarily the case! Maybe the Saint Bernard’s genes actually win out and the puppies don’t bark much, or maybe the Labrador’s genes are more dominant and the puppies bark a lot. Or maybe some don’t bark much and others bark a lot more!
Which one of the following uses flawed reasoning that most closely resembles the flawed reasoning used in the argument above?
All students who study diligently make good grades. But some students who do not study diligently also make good grades. Jane studies somewhat diligently. Therefore, Jane makes somewhat good grades.
Wrong flaw. Unlike the stimulus, (A) doesn’t name two categories and define their traits as distinct; rather, (A) names two categories (diligent studiers and non diligent studiers) and defines their traits as sometimes the same (diligent studiers make good grades, and non diligent studiers sometimes do, too). (A) isn’t valid because there’s no evidence that somewhat diligent studiers make somewhat good grades, but the stimulus’ flaw is different: it’s about an assumption regarding the outcome of mixing two traits together.
All type A chemicals are extremely toxic to human beings. All type B chemicals are nontoxic to human beings. This household cleaner is a mixture of a type A chemical and a type B chemical. Therefore, this household cleaner is moderately toxic.
This argument rests on the idea that chemicals with differing traits combine to produce an average of their traits. Type A chemicals are extremely toxic, and Type B chemicals are nontoxic, so a combination must be moderately toxic. This is the same variation of the cookie-cutter part vs. whole flaw: the author assumes that combining two parts together forms a whole whose traits must sit squarely between the original parts.
All students at Hanson School live in Green County. All students at Edwards School live in Winn County. Members of the Perry family attend both Hanson and Edwards. Therefore, some members of the Perry family live in Green County and some live in Winn County.
No flaw. This is a valid argument! If all students at Hanson School live in Green County, then anyone in the Perry family who attends Hanson School must live in Green County. Similarly, if all students at Edwards School live in Winn County, then anyone in the Perry family who attends Edwards school must live in Winn County.
All transcriptionists know shorthand. All engineers know calculus. Bob has worked both as a transcriptionist and as an engineer. Therefore, Bob knows both shorthand and calculus.
No flaw. This is a valid argument! If all transcriptionists know shorthand and all engineers know calculus, and Bob has been both a transcriptionist and an engineer, then he must know both shorthand and calculus (assuming, of course, that he hasn’t forgotten these skills)!
All of Kenisha's dresses are very well made. All of Connie's dresses are very badly made. Half of the dresses in this closet are very well made, and half of them are very badly made. Therefore, half of the dresses in this closet are Kenisha's and half of them are Connie's.
Wrong flaw. Unlike the stimulus, where the flaw is a variation on the part vs. whole flaw, this argument rests on the flaw of mistaking a sufficient condition for a necessary condition. It’s true that all of Kenisha’s dresses are well made, but that doesn’t mean all well-made dresses are Kenisha’s! Similarly, all of Connie’s dresses are badly made, but that doesn’t mean all badly made dresses are Connie’s! We can’t determine the ownership of these specific dresses based on the premises.
Answer five questions and we'll estimate your score.
It takes about five minutes.
Take the free diagnostic