PrepTest 132

Incorrect. The conclusion (and premises) are specifically about etching tools used for engraving, so other tools used for engraving are out of scope.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:

(1) Etching tool → Pin-tipped OR Bladed
(2) Bladed-some-Used for engraving
(3) Bladed-some-not Used for engraving
(4) Pin-tipped → Used for engraving

Therefore: There are more pin-tipped etching tools used for engraving than not.

Answer Anticipation:
This argument has a mix of quantifier statements and conditional statements before heading to a comparative conclusion. That comparison looks at the number of one type of etching tool versus another.

This isn't something discussed all that frequently, but quantifiers aren't about numbers—they're about percentages. Some is equivalent to saying "at least 1%*," and most to saying "at least 51%*." In jumping from premises that are about percentages to a conclusion about numbers—even comparative numbers—this argument is making a jump from a percentage to an amount. That's a classic flaw.

But this argument isn't asking us to point out the flaw! It's asking us to find an answer that allows the conclusion to be properly drawn. How can we reconcile percentages and amounts? The easiest way to do so is to discuss the total size of a group. If you know the total size of a group (or, in this case, the relative size since the conclusion is comparative) and a percentage, you can figure out the amount. We won't actually have to figure out the amount on the LSAT—we just need to know that we can.

So what group sizes (absolute or relative) can we establish here to make sure that the conclusion is validly drawn? It's going to have to be about pin-tipped and bladed etching tools. The conclusion states that more are used for engraving than not, and we know that all pin-tipped etching tools are used for engraving, whereas only some bladed ones are. So any answer that establishes an equivalent or greater number of pin-tipped tools exists than bladed tools will ensure that the balance is in favor of tools used for engraving. There's a more complex answer that involves balancing pin-tipped tools and bladed tools that are used for engraving with bladed tools that aren't, but let's hope it doesn't come to that!

*Note that we're dealing in whole numbers here, which is why we didn't do 50.000000001%. This is the LSAT, not a math test!

Answer Explanation:
All pin-tipped etching tools are used for engraving, and some bladed ones are, as well. If the number of each is equivalent, then the pin-tipped tools get us to 50% used for engraving. Add to that "some" of the bladed tools that are also used for engraving and you're over 50%, justifying the conclusion.

Key Takeaway:
Quantified statements are about percentages—what minimum percentage of a given group has a certain characteristic or falls into another group. These words don't tell us anything about the number of elements, however, and so a conclusion that jumps to numbers (even relative ones like larger or smaller) will be flawed.

Incorrect. This answer doesn't establish anything about the relative number of these tools, so it can't justify a conclusion that one group is bigger than the other.

Incorrect. Without knowing the relative number of pin-tipped and bladed tools, we can't make a call on the conclusion. That said, if anything, this answer cuts against the conclusion.

Incorrect. This answer is an implication of the premises in the stimulus, so it doesn't add anything new.