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Practice LSAT Arguments

In this final article in the lesson series on LSAT Arguments, we present you with some practice LSAT arguments.

This lesson series covers the following articles:

LSAT Arguments: An Introduction
Structure of LSAT Arguments
Finding LSAT Assumptions
Logic on the LSAT: Two Types
Practice LSAT Arguments 

Try your hand at identifying the conclusions, evidence and assumptions in the following arguments for some extra practice with LSAT arguments.

Practice LSAT Arguments

My sister says that her son’s colic was caused by certain proteins and antibodies found in cow’s milk. That isn’t true. I’ve seen plenty of studies that indicate that many breastfed babies who have never drank cow’s milk develop colic as well.

————

A leading education magazine recently ranked Smithtown among the top ten cities with the worst high school dropout rates. The magazine conducted a survey of Smithtown residents and found that one in four residents over the age of 19 failed to complete high school. 

————

One of large SUVs often claim that heavier vehicles are more dangerous and accidents that involve SUVs are more likely to result in fatalities. I think SUVs are actually safer than smaller vehicles. There are more SUVs per driver in the West and in agricultural communities and yet the rate of automobile-related fatalities is much less than in urban areas that typically drive smaller economy cars.

————

25 out of 100 cats who contract feline leukemia will die within six months. There is a vaccine available that is nearly 100 percent effective and the complications from the vaccine result in death only 5 out of 10,000 cases. Clearly everyone should vaccinate their cats against feline leukemia since it is safer to vaccinate them than not.

Identify the conclusion, evidence and assumptions in these arguments before moving onto the following section which will reveal the right answers.

Most of the time the evidence is what is left over once you’ve identified a conclusion. There can be filler, however, so it’s important to be specific. It is particularly important when you work to identify an assumption, especially if you’re trying to build a bridge between the evidence and conclusion. This is the importance of building a paraphrase. In your paraphrase you can reword the evidence and conclusion in similar ways to see what the gaps are and identify assumptions.

Once you have identified the evidence and conclusions, you will almost always need to consider the assumption. It helps to paraphrase the evidence and conclusions in your own words to find similarities between them and to form the bridge that is the unstated assumption. Sometimes a red flag will pop up in your head based on a flawed assumption that the author makes.

Here are the arguments again, only this time we’ve bolded the conclusions and italicized the evidence.

Practice LSAT Argument 1

My sister says that her son’s colic was caused by certain proteins and antibodies found in cow’s milk. That isn’t true. I’ve seen plenty of studies that indicate that many breastfed babies who have never drank cow’s milk develop colic as well.

The tip-off in this argument is the conflicting language. Specifically the (unstated) conclusion is that colic is not caused by proteins and antibodies found in cow’s milk. Why isn’t the first sentence evidence? Because it’s basically stating the conclusion in reverse. The conclusion is that the author’s sister is wrong.

A paraphrase of this argument might be:

Breastfed babies who do not drink cow’s milk get colic.

Thus

Proteins and antibodies found in cow’s milk do not cause colic.

When you are forming a bridge with this argument, you need to consider what is similar and what is dissimilar. There needs to be some link between breastfeeding and the proteins and antibodies found in cow’s milk. The author must be assuming that those proteins and antibodies are not passed on through breast milk if the mother drinks cow’s milk. You might have also identified the red flag by wondering, “what if the mother drinks cow’s milk?”

Practice LSAT Argument 2

A leading education magazine recently ranked Smithtown among the top ten cities with the worst high school dropout rates. The magazine conducted a survey of Smithtown residents and found that one in four residents over the age of 19 failed to complete high school.

The conclusion here is trickier because the author doesn’t take a stand. The author is instead describing the conclusion made by a leading education magazine. The main idea is that Smithtown has a bad dropout rate. The main evidence to focus on here is the drop out rate of Smithtown residents.

A paraphrase of the practice LSAT arguement might look like this:

1/4 of residents are drop outs.

Thus

The city has one of the worst drop out rates.

To form a bridge with this argument you need to link residents to drop out rates. The author (or more specifically the magazine who conducted the survey) must assume that almost all of the residents were schooled in Smithtown . You might have thought of the red flag in this argument by wondering, “what if these one in four residents moved here from somewhere else?”

Practice LSAT Argument 3

One of large SUVs often claim that heavier vehicles are more dangerous and accidents that involve SUVs are more likely to result in fatalities. I think SUVs are actually safer than smaller vehicles. There are more SUVs per driver in the West and in agricultural communities and yet the rate of automobile-related fatalities is much less than in urban areas that typically drive smaller economy cars.

Here the author does take a strong stand. We know this from the conflicting language and from the words “I think.” Conflict always points to what’s at stake in an argument. The author is contradicting a popularly held criticism of SUVs, but that criticism is not part of the author’s own evidence.

A paraphrase of this practice LSAT argument could be:

The proportion of SUV drivers is higher in the West

and yet they have fewer fatalities.

Thus

SUVs are safe.

The red flag that pops up here is that the author is trying to discuss two types of facts as if they are the same. The author has a problem with the way the numbers are presented. One part of the evidence deals with percentages while another deals with totals. That is an error in reasoning. Couldn’t it be the case that there are fewer fatalities in the in the West simply because there are fewer people, or that those people don’t face the same traffic density you might find in urban areas? The author must be assuming that the number of fatalities is also proportional by population density.

Practice LSAT Argument 4

25 out of 100 cats who contract feline leukemia will die within six months. There is a vaccine available that is nearly 100 percent effective and the complications from the vaccine result in death only 5 out of 10,000 cases. Clearly everyone should vaccinate their cats against feline leukemia since it is safer to vaccinate them than not.

The clue word here is “clearly,” which signals the conclusion. This one is straightforward, two pieces of evidence that lead to a conclusion.

A paraphrase of this practice LSAT argument could be:

25/100 cats with leukemia will die.

5/10,000 cats who are vaccinated will die.

Thus

It’s a better bet to vaccinate.

This author also has a numbers problem. The author is trying to compare the rate of cats with leukemia to the the rate of the entire population of cats. How many cats actually contract leukemia. If that number is less than 5 in 10,000 it would actually be safer not to vaccinate cats. The author is assuming that those rates are similar. When you are dealing with statistics on the LSAT test, you will often find a problem with the numbers not matching up. Look there first if nothing jumps out at you.

LSAT Arguments Summary Tips

  • All arguments have three parts: a conclusion, a set of premises, and a set of assumptions
  • An inference is something the author doesn’t say, but wants you to get out of the argument.
  • An inference can be an unstated premise (assumption), or a conclusion (main idea).
  • The conclusion is the main point the author wants to make and often follows a clue word such as “therefore,” or “so.”
  • Premises are facts supporting the argument. They answer the “why” of the conclusion and often follow clue words such as “because,” or “since.”
  • Assumptions are unstated premises. If the premises are true and the conclusion is true, then the assumptions must also be true.
  • Assumptions are the weak link in an argument. Most Logical Reasoning questions revolve around the assumption.
  • To find the assumption, ask what the weak link or the logical gap is in the argument. The assumption must bridge that gap.
  • Paraphrase each argument in your own words. It’s easier to remember your words than it is to reread a long difficult casual argument.

That concludes our lesson series on LSAT Arguments. That’s a lot to absorb, but it will get easier as you see more arguments. Now return to TestSherpa’s main LSAT page to find more lessons for the LSAT Test.

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