#19 - The conventional process for tanning leather uses

[Administrator]

Complete Question Explanation

Assumption. The correct answer choice is (D)

According to the stimulus, leather can either be tanned using chemicals catalyst or biological catalysts. It costs about the same to use either process, except for the cost of waste disposal, which is a major consideration. Twenty percent less waste is produced using the biological catalysts. Therefore, the stimulus concludes, it is less costly to tan leather using the biological catalysts.

The question stem asks for the assumption that is necessary for the conclusion to logically be drawn from the premises. In this case, the author made a logical jump in the argument. Though we know that the biological tanning produces less waste, and waste disposal is a significant portion of the overall cost of tanning leather, the author does not clarify how the cost of disposing of biological waste compares to the cost of disposing of chemical waste. That information is needed in order to draw the conclusion that it is cheaper to use biological catalysts to tan leather.

Answer choice (A): The quality of the leather produced is irrelevant to the overall cost of tanning the leather. The conclusion, and in fact the argument as a whole, is limited to considerations of cost. Therefore, an answer choice, like this one, about quality, is not necessary for the argument about cost.

Answer choice (B): This answer choice addresses the issue of cost, stating that the biological catalysts are less costly by weight than the chemical catalysts. However, it is not clear that the tanning requires the same amount of biological catalyst as chemical. Further, the stimulus already stated that the cost for using biological and chemical catalysts is equivalent, except for the cost of waste disposal.

Answer choice (C): Like in answer choice (A), this answer choice is about something other than cost. In this case, the answer choice provides information about the efficacy of using one technique over the other. Since the conclusion of the argument was limited to cost, this answer choice will not impact the conclusion.

Answer choice (D): This is the correct answer choice. This answer choice states that disposal of the waste produced using a biological catalyst is not more expensive than disposing of waste using a chemical catalyst. We can use the Assumption Negation technique to verify that this answer choice is correct. The negated answer choice would read “Disposal of tanning waste produced with biological catalysts does cost significantly more than disposal of the same amount of waste produced with the conventional process.” This would weaken the conclusion, because even though the biological process produces less waste, it would be more costly to dispose of it. Thus, since the negated form of the answer choice weakens the conclusion, we know the answer choice is a necessary assumption.

Answer choice (E): The stimulus already ruled out other cost factors with the catchall statement that tanning using either method costs about the same if waste disposal is factored out. Therefore, information about the details of other cost factors are not relevant to the final conclusion, because they have already been considered by the author.

[mN2mmvf]

Hi,

I understand the rationale for (D), but not quite for why (E) is incorrect. Why is it that just because labor costs fall within the catchall sentence in the premise, it means that it's not still an assumption required by the argument? It's compatible with the catchall statement and is itself also required by the argument, or else it would conflict with the catchall and weaken the argument.

Related aside: can a correct weakening answer every simply directly contradict the true of a stated premise? (e.g., premise, "the sky is blue," weakening answer, "the sky is actually not blue")

[Adam Tyson]

Happy to help, mN2mmvf! First, it is indeed important that the catchall claim about all costs, other than waste, being accounted for must include labor costs, because that means he is not making any assumptions about labor. Rather, he has a premise that covers labor. In other words, he already said it, and assumptions are always things the author did NOT say.

By analogy, if I were to say that all mammals on earth need air and water, and horses are mammals, am I assuming that horses need air and water? Nope - I'm not assuming it, I'm SAYING it. Big difference! That's why E is not an assumption of the argument, but is instead built in to the premises of the argument.

As to your second question, we do occasionally attack premises, but not often. Most of the time we accept the premises as true and focus our weaken attacks on the link between those premises and the conclusion. When we do attack premises it is usually in a weaken-Except question, where we need four different ways to weaken the argument to be our wrong answers, and so we might in some way contradict a premise. Even then, we are usually doing more than just saying "that's false", but are adding new info to suggest that the premise may be based on a bad assumption of have some other inherent flaw.

Keep at it!

[mN2mmvf]

Thanks for the reminder - "assumptions are always things the author did NOT say." That solves it.

[akanshalsat]

Hello, I still don't get how D is an assumption of the argument... Saying that their disposal of tanning waste is relatively same doesnt make sense.. what is that saying?

[James Finch]

Hi Akansha,

The difficulty with a lot of Assumptions is that they are almost too obvious to notice. The test makers expect the test takers to make these same assumptions, and then believe this information to be either explicitly given by the stimulus or otherwise known or inferred. However, when carefully parsed the information is not present as a premise in the stimulus, but instead assumed by the conclusion. Breaking it down:

Premises: Conventional chemicals and Biological Catalysts cost the same to tan leather, excluding waste disposal costs. Biological catalysts only produce 80% the waste that conventional chemicals do. Waste disposal is "substantial" part of cost of leather tanning.

Conclusion: Tanning with biological catalysts is cheaper than with conventional chemicals.

What are we missing? We don't know the total cost of waste disposal between the two types, which is the determinant in which method costs more. All we know is that one method produces 20% less waste than another, but if biological catalysts' waste cost 50% more than conventional chemicals to dispose of, then the conclusion would be false. So the argument assumes that the costs are roughly the same, as (D) says.

We can also use the Assumption Negation technique to test it:

Bio Costs Signicantly Higher Bio tanning is not less costly

Hope this clears things up!