Q25 - Each major earthquake

[smiller]

Question Type:
Match the Flaw

Stimulus Breakdown:
Premise: quake → tremors
Premise: tremors
Conclusion: quake

Answer Anticipation:
It’s an illegal reversal! Run! No, don’t run. Just look at each answer choice and eliminate any with clear mismatches, like an answer with conclusion that states something “should” happen, or that either one thing or another will happen.

Unfortunately there aren’t many clear mismatches in the answers for this question, so we need to look more closely at the conditional statements in the answers.

Correct answer:
(E)

Answer choice analysis:
(A) No reversal (valid contrapositive):
TS → H
~ H
———
~ T

(B) No reversal:
HS → RO
HS
———
RO

(C) Wrong flaw: This argument shifts from a premise about planets other than Earth to a conclusion about meteors bombarding Earth. This is called the Armageddon fallacy, named after the famous 1998 movie staring Bruce Willis. No, it’s not. We just made that up. What’s important is that this shift from other planets to Earth introduces a potential flaw that wasn’t part of our original argument.

(D) No reversal:
NNS → Extinction
NNS
———
Extinction

(E) Correct (same flaw):
Outbreak → infected wildlife
infected wildlife
———
Outbreak


Takeaway/Pattern:
Arguments in Matching questions are frequently based on conditional logic. Diagramming can be useful if it helps you keep track of the statements and spot conditional logic flaws.

#officialexplanation

[aminay777]

Hello, I chose answer B and despite reading your explanation, can't figure out why B is incorrect.

Instead of using HS → RO, does it not make sense to state it as the reverse?

The premise states: Each major earthquake in this region has been preceded by a series of minor tremors.
Could you not reword option B to state: This river's overflowing has been preceded by a winter with heavy snowfall and diagram it as
RO → HS?

Looking forward to your response.

Amina

[smiller]

Could you not reword option B to state: This river's overflowing has been preceded by a winter with heavy snowfall and diagram it as
RO → HS?

That's a good question. However, what you're suggesting is not a correct way to reword that sentence. The phrase "in every" in the original sentence tells us that we can interpret this as a conditional statement. That phrase also tells us the direction of the logic. Consider a similar sentence:

There is a TV in every room of my house.

Does this mean TV → RMH? No. This sentence doesn't tell us that every TV in existence is in a room of my house. The correct way to diagram this is RMH → TV. There might be TVs in other people's houses. Likewise, the river might have overflowed at other times of year, besides in the spring thaw after a winter with high snowfall. That's why we diagram the statement in (B) as HS → RO.

[krisk743]

I don't think the explanation for A is correct. You said it's a valid contrapositive but it is not.

TS > H
The reasoning is since ~TS

and concludes thus, ~H

That's illegal negation. So is a/c A wrong because it isn't necessarily a reversal but a negated reversal? (even though I would argue that shouldn't be a reason why it isn't the correct a/c)

Question Type:
Match the Flaw

Stimulus Breakdown:
Premise: quake → tremors
Premise: tremors
Conclusion: quake

Answer Anticipation:
It’s an illegal reversal! Run! No, don’t run. Just look at each answer choice and eliminate any with clear mismatches, like an answer with conclusion that states something “should” happen, or that either one thing or another will happen.

Unfortunately there aren’t many clear mismatches in the answers for this question, so we need to look more closely at the conditional statements in the answers.

Correct answer:
(E)

Answer choice analysis:
(A) No reversal (valid contrapositive):
TS → H
~ H
———
~ T

(B) No reversal:
HS → RO
HS
———
RO

(C) Wrong flaw: This argument shifts from a premise about planets other than Earth to a conclusion about meteors bombarding Earth. This is called the Armageddon fallacy, named after the famous 1998 movie staring Bruce Willis. No, it’s not. We just made that up. What’s important is that this shift from other planets to Earth introduces a potential flaw that wasn’t part of our original argument.

(D) No reversal:
NNS → Extinction
NNS
———
Extinction

(E) Correct (same flaw):
Outbreak → infected wildlife
infected wildlife
———
Outbreak


Takeaway/Pattern:
Arguments in Matching questions are frequently based on conditional logic. Diagramming can be useful if it helps you keep track of the statements and spot conditional logic flaws.

#officialexplanation

[AnnaC659]

Hi,

In the explanation above it says:
premise: earthquake -> tremors
conclusion: tremors -> earthquake

But I thought it was:
premise: tremors -> earthquake
conclusion: tremors -> earthquake
And thought it was correlation/causation flaw.

The stimulus says "each major earthquake in this region has been preceded by a series of minor tremors." So I understood it as 'minor tremors' came before 'each major earthquake,' hence tremor -> earthquake.

Please help me understand?

Thank you in advance!

[ohthatpatrick]

krisk743, thanks for catching that! I'm going to go back and edit the post.

Conditional logic is about certainty, not chronology. It doesn't matter which one comes first. It only matters which one provides certainty about the other.

If we say, "Every student who takes Bio201 had to first take Bio101", then clearly we know that Bio101 comes first chronologically.

But consider which one provides certainty about the other:
if someone took Bio101, are you certain that they are taking Bio201?"
vs.
if someone is taking Bio201, are you certain that they took Bio101?"

The latter case is the one where we have certainty, so we could write a conditional logic statement that says,
"If you're taking Bio201, I know that you took Bio101"
Bio 201 --> Bio 101

Similarly, for this region in Q25,
if there was a major quake, are we certain there were minor tremors before?
vs.
if there were minor tremors, are we certain that they were followed by a major quake?

We're only sure of the former case.
Major quake --> Minor tremors before

------------------
If you've memorized your Conditional Logic Words, you'd just see "Each major earthquake" and think LEFT SIDE.

LEFT SIDE (if, when, whenever, the only, any, each, every, all, no)
RIGHT SIDE (only if, only, ensures, guarantees, requires, must)
UNLESS / UNTIL / WITHOUT = “if not”
BICONDITIONAL
(if and only if, then and only then, when and only when, “if X, then ___ . Otherwise, ___ .”)
NEITHER/NOR = “not this and not that”
NESTED UNLESS = “If then A, then B, unless C” --> “If A and not-C, then B”
-------------------

We wouldn't be able to call this argument correlation vs. causality because there's no causal verb ever used.

The author concludes that because Y has always preceded X, Y will again precede X in this recent case.

The author hasn't ever said that Y causes X. He might well believe that Z always causes Y and X (X just happens slightly later).

If the conditional logic had been in the order you were thinking, we would only accuse this author of making a TEMPORAL FLAW ... i.e., assuming that a pattern that has been true before will be true again.

Hope this helps.

[JoyC484]

krisk743, thanks for catching that! I'm going to go back and edit the post.

Conditional logic is about certainty, not chronology. It doesn't matter which one comes first. It only matters which one provides certainty about the other.

If we say, "Every student who takes Bio201 had to first take Bio101", then clearly we know that Bio101 comes first chronologically.

But consider which one provides certainty about the other:
if someone took Bio101, are you certain that they are taking Bio201?"
vs.
if someone is taking Bio201, are you certain that they took Bio101?"

The latter case is the one where we have certainty, so we could write a conditional logic statement that says,
"If you're taking Bio201, I know that you took Bio101"
Bio 201 --> Bio 101

Similarly, for this region in Q25,
if there was a major quake, are we certain there were minor tremors before?
vs.
if there were minor tremors, are we certain that they were followed by a major quake?

We're only sure of the former case.
Major quake --> Minor tremors before

------------------
If you've memorized your Conditional Logic Words, you'd just see "Each major earthquake" and think LEFT SIDE.

LEFT SIDE (if, when, whenever, the only, any, each, every, all, no)
RIGHT SIDE (only if, only, ensures, guarantees, requires, must)
UNLESS / UNTIL / WITHOUT = “if not”
BICONDITIONAL
(if and only if, then and only then, when and only when, “if X, then ___ . Otherwise, ___ .”)
NEITHER/NOR = “not this and not that”
NESTED UNLESS = “If then A, then B, unless C” --> “If A and not-C, then B”
-------------------

We wouldn't be able to call this argument correlation vs. causality because there's no causal verb ever used.

The author concludes that because Y has always preceded X, Y will again precede X in this recent case.

The author hasn't ever said that Y causes X. He might well believe that Z always causes Y and X (X just happens slightly later).

If the conditional logic had been in the order you were thinking, we would only accuse this author of making a TEMPORAL FLAW ... i.e., assuming that a pattern that has been true before will be true again.

Hope this helps.

So does it mean that because the argument use "has been", aka predict future issues from past trend, so it is not a formal logic and we cannot use contraposition?

[abrenza123]

I KNOW i have run into trap answers/errors of logic in LR answers in flaw/paradox questions where the time shift comes into play... I saw a time shift error in this argument, because I thought it would be wrong to assume that just because earthquakes in this region have been preceded by tremors in the past that they will be in the future, as a conditional would imply. I understand that doesn't totally come into play in this question, but in general is that safe to say??? Also, there could be instances where tremors occur and are not followed by earthquakes...

I initially chose B, but is it correct in saying that B isn't necessarily valid without more information - just because in the past it has always flooded after high snowfall doesn't mean it will in the future... even though "record high" does make strengthen that possibility. To me, B is incorrect because of the structure - the stimulus isn't saying that every time the region has tremors, it has earthquakes, therefore

What if B said, "The river has flooded every spring following heavy snowfall. there has been flooding in the river this spring, therefore there must have been heavy snowfall"?... Would that be showing the same type of flaw as in stimulus? It matches the conditionality shown in the explanation, =but would it incorrect because it is making a hypo about something that has already happened vs. something that will happen in the future??

Thank you!!!

[ohthatpatrick]

Yes, this is definitely making a "time shift" error (I called it the TEMPORAL FLAW in my posts).

It's the idea that "because something was true before, it will be true again".
But there's also a conditional-feeling reversal happening here.

A more-valid argument would sound like:
Each major quake has been preceded by tremors. Since we recently experienced a major quake, there were almost certainly tremors right before that.

Consider this data set:
tremors, no quake
tremors, no quake
no tremors, no quake
tremors, quake
tremors, no quake
tremors, no quake
tremors, quake
no tremors, no quake

It's true to say that every time there was a quake (both times), there were tremors before it.

But ... if we know there are tremors, would we EXPECT a quake to follow?
No. Of the six times when there were tremors, only twice did a quake follow (33% of the time).

So the flaw here does feel like a "since it happened before, it'll happen again", but there's also a statistical element to it that feels like ..
EVEN THOUGH ..... every X had a Y that came before it
THAT DOESN'T MEAN THAT .... Y's are normally followed by X's.

To use a gross example,
"Every time the toilet got clogged was preceded by Reggie taking a #2. Since Reggie just went into the bathroom to take a #2, the toilet will be clogged in the near future."

Reggie may be the only one who's ever clogged the toilet, but that doesn't mean that every time he uses the toilet we should expect clogging.

The problem with (B) vs. the original, is that in the original the "Each / every / all" is modifying the 2nd event.

All quakes (2nd event) are preceded by tremors (1st event).

In (B), it says that
every time we have a snowy winter (1st), the river overflows during the spring thaw (2nd).

If you prefer symbolic stuff,
ORIGINAL
every 2nd thing was preceded by a 1st thing.
the 1st thing happened, thus the 2nd is a'comin.

CHOICE (B)
every time a 1st thing has happened, a 2nd thing has.
The 1st thing happened, thus the 2nd is a'comin.

If you wanted (B) to match the original, you have to fix the first sentence:
Every time the river has overflowed in the spring has been preceded by a snowy winter.

Hope this helps.