#21 - Consumer magazine: Because front-loading washers use

[Administrator]

Complete Question Explanation

Assumption. The correct answer choice is (D)

The consumer magazine article describes a potential difficulty with front-loading clothes washers. Because they use less water than top-loading washers, ordinary powder detergent does not dissolve readily in the front-loading washers. The article concludes that in order to get clothes really clean in front-loading washers, you need to use a detergent formulated especially for front-loading washers, instead of ordinary powder detergent.

Here is how the argument proceeds:

• Premise: Front-loading washers use less water than top-loading washers.
  
  Sub-Conclusion: Ordinary powder detergent does not dissolve readily in front-loading washers.
  
  Conclusion: To get clothes really clean in a front-loading machine, you need to use a detergent formulated especially for front-loading washers, instead of ordinary powder detergent.

This is an Assumption question. Your task is to select the answer choice containing information required for the conclusion to be valid. It is apparent from the context of the stimulus that the detergent formulated for front-loading washers will dissolve more readily in less water than is required for detergent to dissolve in top-loading washers. So, expressly adding that information to the conclusion, the conclusion states that to get clothes really clean in a front-loading washer, you need to use a detergent formulated to dissolve readily in the amount of water used by front-loading washers.

However, a logical gap remains in the argument. No premise establishes that detergent dissolving readily is required to get clothes really clean. The concept of getting clothes really clean appears for the first time in the conclusion. So, it is unsupported by the stimulus and is a logical gap in the argument.

Your prephrase is that this is a Supporter Assumption question, in which the correct answer choice will provide a link between the new information in the conclusion, i.e., getting clothes really clean, and the concept of detergent formulated to dissolve readily in front-loading washers.

Answer choice (A): The amount of water used by top-loading washing machines is irrelevant to the conclusion, which dealt only with what is required to get clothes really clean in a front-loading washer.

Answer choice (B): This is an attractive answer choice, because the stimulus implies that laundry detergent formulated especially for front-loading machines is designed to dissolve more readily in the lesser amount of water used by those machines. However, this answer choice goes farther than it might initially appear, stating a comparison that is not required for the conclusion to be valid. This choice states that a laundry detergent formulated especially for front-loading washers dissolves more readily in a front-loading washer than in a top-loading washer. This comparison is not required for the conclusion to be valid. Rather, for the conclusion, it simply must be the case that detergent formulated for the front-loading washer dissolves readily in it, while the ordinary detergent does not.

Answer choice (C): For this answer choice to be required for the conclusion, the evidence would have to establish that ordinary detergent does not dissolve readily in either top-loading or front-loading machines, and that detergent must be formulated specifically for use in top-loading machines just like detergent must be formulated specifically for front-loading machines.

Answer choice (D): This is the correct answer choice. This answer choice addresses the new information in the stimulus: what is required to get clothes really clean. This information establishes a conditional relationship, in which a laundry detergent dissolving readily in a washer is required for a laundry detergent to get clothes really clean in a washer.

• laundry detergent gets clothes really clean laundry detergent dissolves readily

If this answer choice were logically negated, such that a laundry detergent dissolving readily in a washer is no truly necessary for the laundry detergent to get clothes really clean in the washer, then the conclusion would be proven invalid.

Answer choice (E): It is not the amount of water used in the machine that determines whether the clothes can be made really clean. Rather it is the ability of the detergent to dissolve readily. The amount of water in the machine was pertinent to the argument only as an indication of whether the detergent could dissolve readily.

[15veries]

Hi,

I chose D but I am not so sure why B is wrong.
It maybe correct if it is sufficient assumption, but not necessary assumption?
Also maybe because it does not have to compare with top-loading washers?

btw
I know negation test is a good test but I don't really like it so I would like to find out why correct one is correct without using it first...

[Jonathan Evans]

Hi, 15veries,

In fact, answer choice B is neither necessary nor sufficient for a valid conclusion. Let's symbolize the reasoning here to illustrate:

Premise: OPD DR

Conclusion: CRC OPD & SFD

In other words, you must provide an assumption that shows that ordinary powder detergent is in fact necessary for your conclusion to be valid. Here, you could show that given the use of ordinary powder detergent, it is impossible to get clothes really clean. You are showing that a purported necessary condition is in fact necessary.

To justify this conclusion you would need to show that really clean clothes in a front loader always implies both ordinary powder detergent and the use of specially formulated detergent. That is not the task here, and B does not accomplish it for you. B is in fact irrelevant. The relative speed at which a specially formulated detergent dissolves in one type of washer instead of the other is immaterial.

Thus, you are correct:

Also maybe because it does not have to compare with top-loading washers?

Now, you do not need to use the negation test to get the answer right on an assumption question. Without the negation test, you will need to work on getting a very accurate prephrase from the stimulus. However, perhaps you should consider practicing the negation test so that it becomes more of a natural process for you. I find that I almost automatically rephrase contender answer choices on assumption problems in their negated forms. This way I have a quick and accurate way to determine whether or not the conclusion is valid. I do this process both on easy and hard questions, and as you will find, on harder assumption questions, the negation test becomes increasingly essential to know that you have selected the credited response.

[ShannonOh22]

Seeing as this is a necessary assumption question, and we are supposed to be able to use the negation technique to verify the correct answer, I am still not seeing how B is incorrect.

B): "A laundry detergent formulated especially for front-loading washers dissolves more readily in them than it does in top-loading washers."
B negated becomes "A laundry detergent formulated especially for front-loading washers does NOT dissolve more readily in them than it does in top-loading washers"

The statement above, if added to the stimulus, would indeed ruin the author's argument. The conclusion is about getting clothes really clean, and in order to do this in a front-loading washer, the detergent needs to dissolve readily.

On the other hand...

D states: "A laundry detergent does not get clothes really clean in a washer unless it dissolves readily in it."

Negated ->
Even if detergent does not dissolve readily in a washer, clothes may/can still get really clean.

Wouldn't the logical opposite of "does not" be "does not not", therefore "possibly does do", therefore "can/may/might"?

If so, D would surely weaken the argument, but it would not destroy it because of the presence of "can/may/might". Please let me know where I'm going wrong on this...I'm flummoxed!

[KelseyWoods]

Hi Shannon!

Assumption questions are one of the trickiest LR types for a variety of reasons. One thing that can make them tricky is that sometimes the assumption the author is making seems so obvious that we end up making the assumption right along with the author! But go back and re-read that stimulus. Where in the stimulus does it say that to get clothes clean, your laundry detergent needs to dissolve readily? It doesn't!

So now that we know that we don't actually have any stated evidence that readily dissolving is necessary for really clean clothes, look at your negation for answer choice (B) again: "A laundry detergent formulated especially for front-loading washers does NOT dissolve more readily in them than it does in top-loading washers." This actually has no effect on our argument above because we don't know whether detergent needs to dissolve readily to get clothes really clean.

Answer choice (D), however, explicitly states the assumption made by the author--which is the same assumption you made when determining that the negation of (B) attacked the argument! If we negate (D) to basically say that you can get clothes clean without having detergent that readily dissolves, that would attack the argument that a detergent formulated for front-loading washers is necessary to get clothes really clean. Because if it's possible to get clothes clean without detergent that readily dissolves, then we don't actually NEED specifically formulated detergent. A "can" is enough to destroy an argument that is very certain. If it's "possible" to get clothes clean without readily dissolving, that destroys the argument that it's "impossible" to get clothes clean without specific detergent.

Hope this helps!

Best,
Kelsey

[plzhelpme101]

Can someone please help me understand how C is incorrect? If this is a necessary assumption question, then this means that if the conclusion is true, the answer you choose must be true, right? So if to get clothes really clean in a front loading machine, you need to use a detergent formulated for that machine, then how is C false? It literally restates this. You can infer that this is also true for top-loading machines since they use their own special powder according to the stimulus.

Furthermore, how do you even prove D? The stimulus doesn’t directly say this. It sort of hints at it but I don’t see how it can be proven from the stimulus. This question is driving me insane. Any help is appreciated

[plzhelpme101]

Can someone please help me understand how C is incorrect? If this is a necessary assumption question, then this means that if the conclusion is true, the answer you choose must be true, right? So if to get clothes really clean in a front loading machine, you need to use a detergent formulated for that machine, then how is C false? It literally restates this. You can infer that this is also true for top-loading machines since they use their own special powder according to the stimulus.

Furthermore, how do you even prove D? The stimulus doesn’t directly say this. It sort of hints at it but I don’t see how it can be proven from the stimulus. This question is driving me insane. Any help is appreciated

I would add that D would definitely be a good answer if it were a sufficient assumption question, but this doesn’t ask you to prove a conclusion so shouldn’t it be a necessary assumption?

[Paul Marsh]

Hi plzhelpme101! Great username.

You are exactly correct that this is a necessary assumption question. You are also correct that in a necessary assumption question if the conclusion is true, our right answer must be true as well.

Our conclusion for our argument is "to get clothes really clean in a front-loading machine you need to use a detergent formulated especially for front-loading washers". You say that Answer Choice C "literally restates" that conclusion, but that's not quite accurate. Let's restate C so that it sounds as close to our conclusion as possible: "to get clothes really clean in a washing machine you need to use a detergent formulated especially for that machine". That looks very similar to our conclusion, but it's not quite the same! What's different? C has eliminated the "front-loading" portion of our conclusion. In effect C is saying that any washing machine can only get clothes really clean with a detergent formulated especially for that machine. That's a much stronger claim than the one in our conclusion, which is specifically addressing only front-loading washers. If our conclusion is true, the stronger claim in C does not necessarily have to be true as well.

We can take a couple lessons from your mistake. First, watch out for those Shell Game answer choices. When an answer choice seems to directly quote from the passage but changes one key word or phrase, make sure they're not pulling a fast one on you. Second, be very cautious about strongly worded answer choices in Assumption questions. It is uncommon that everything about a "strong" answer choice will need to be true, and so they typically make poor Assumption answers. An answer choice like C that is essentially starting out by saying "Any washing machine can only..." is asking for trouble from the start.

As for Answer Choice D. You say, "I don't see how it can be proven by the stimulus". That is potentially a very misleading way to think about Assumption questions. Our right answer for Assumption questions is not necessarily proven by the stimulus, but rather something that needs to be true in order for the conclusion to make sense. Take the following argument for example: "I am cranky whenever it's hot. It's always hot in Texas. Therefore, whenever I'm in Austin, I am cranky". That argument seems to be assuming that Austin is in Texas. Therefore, a good necessary assumption answer choice for that argument could be: "The Austin referenced in the argument is not located in Canada". Is that answer choice "proven" by the stimulus? Absolutely not. But does it need to be true in order for the argument to make any sense? Yes! It's the same situation in our stimulus for this problem. The premise tells us that ordinary powder detergent doesn't dissolve in front-loading washers. The conclusion then says that to get clothes really clean, you have to use a special detergent rather than ordinary powder detergent. In order for that conclusion to make any sense at all, it has to be true that the non-dissolving detergent doesn't get the job done. If D was not true (this is the Negation Test), and a non-dissolving detergent could clean clothes just fine, then the conclusion wouldn't make any sense. So just to re-iterate, to find our right answer for necessary assumption questions we're not looking for what's proven by the stimulus, but rather something that needs to be true in order for the conclusion to make sense.

As to your second post - you're right that D is in fact a sufficient assumption for this particular argument (so it would be a good answer for a Justify question). It just also so happens to be a necessary assumption! This happy coincidence occurs sometimes on Assumption/Justify questions, but it's good to keep the two question types separate as it's more common for our right answer to be a sufficient or necessary assumption but not both.

Hope that helps!

[Dancingbambarina]

Why are we not dealing with causality here instead of conditionality? It seems that special detergent directly causes something to occur, no?

Thanks!

[Adam Tyson]

The argument itself is neither causal nor conditional, but the nature of the question directs us to think in conditional terms. Assumptions, as we call them, are also sometimes referred to as Necessary Assumptions. That's because of the conditional nature of the relationship between the argument and the correct answer choice. If the argument is valid, the assumption must be true. That's why you see so much conditional analysis in this thread, Dancingbambarina. It's not because the argument is conditional, but because the argument is sufficient to make the correct answer necessary, and the wrong answers are not necessary.

Even in a causal argument, we see this conditional relationship between the argument and the assumptions. For example, IF the author concludes that A is the sole cause of B, THEN they must assume that C is not a cause of B.