Is there a causal relationship between smoking and lung cancer?

Question

(1) ﻿﻿﻿﻿Research consistently shows a strong correlation between smoking and the development of lung cancer

(2) ﻿﻿﻿﻿Some medical researchers support a proposed mechanism by which smoking could cause lung cancer.

ID: 700322

Source: OG 2025-25 Code: 700322

GMATNinja · Accepted Answer

Well, this is a weird one, but weird is not uncommon these days.

We're asked if there's a causal relationship between smoking and lung cancer -- in other words, does smoking cause lung cancer? Straightforward enough. If you've taken a statistics class, you're probably very tired of hearing that correlation is not causation, but... well, correlation is not causation. The fact that smoking and lung cancer are correlated doesn't mean one causes the other. Maybe drinking bourbon causes lung cancer and people who smoke are more likely to drink bourbon. Maybe people who have lung cancer are more likely to start smoking after their diagnosis. We simply don't know. So this statement is not sufficient. Okay, great. So there's a proposed mechanism, meaning that there's some theoretical way smoking could cause lung cancer. Is there any evidence to support that the proposed mechanism is, you know, correct? We don't know. We know that "some" researchers support the "proposed" mechanism, but have no idea whether it's actually correct. So this statement is insufficient, too. Taken together, all we have is a correlation -- which isn't causation -- and a theoretical mechanism, which isn't actual evidence. So even together, the statements are not sufficient. The answer is (E). I hope that helps!

GMATinsight · Answer

Is there a causal relationship between smoking and lung cancer?

(1) Research consistently shows a strong correlation between smoking and the development of lung cancer.

(2) Some medical researchers support a proposed mechanism by which smoking could cause lung cancer.

Source: OG 2025-25 Code: 700322

OFFICIAL EXPLANATION

Inference

(1) Research-based evidence has consistently shown a high positive correlation between smoking and lung cancer. A strong positive correlation between two factors P and Q indicates that there is a similar pattern of variation in data for P and data for Q (the degree of similarity can vary). For example, long-term data might show that as smoking increases in a population, the data regarding the incidence of lung cancer increases in tandem. Over several years, if the data regarding smoking in a population decreases, the data for lung cancer might also decrease. In both cases, a positive correlation occurs. But such a statistical pattern, by itself, can, at best, suggest some association or dependency, direct or indirect, between the two factors smoking and lung cancer. But correlation evidence, by itself, provides no proof of a causal relationship; NOT sufficient.

(2) The information provided is insufficiently specific to sustain a claim that smoking is causally related to lung cancer. What (2) indicates is a hypothesis proposed by some researchers, but no information is provided to indicate confirmation of that hypothesis; NOT sufficient.

The correct answer is E; both statements together are still not sufficient.

sreehere · Answer

I agree the answer is E.

But I have some doubts about the inference from Statement I. The statement just says "strong correlation". Does "strong correlation" necessarily indicate "high positive correlation"?

kop18 · Answer

I agree..... I do not think a strong correlation should be inferred as high postive correltaion. It's commonsensical to say that there won't be a negative correlation between the two because of a lot of smoking would not decrease the risk of cancer but again it's outside knowledge that we have to bring in order to infer that the correlation is positive. Don't u think  GMATinsight ?

RJ_Joker · Answer

GMATNinja  requesting your explanation for the same. How come its D. Why not B?

anish0953 · Answer

what do you mean by casual relationship here

hughng92 · Answer

If you've taken a statistics class, you're probably very tired of hearing that correlation is not causation, but... well, correlation is not causation.

The fact that smoking and lung cancer are correlated doesn't mean one causes the other. Maybe drinking bourbon causes lung cancer and people who smoke are more likely to drink bourbon. Maybe people who have lung cancer are more likely to start smoking after their diagnosis.

We simply don't know. So this statement is not sufficient.

﻿﻿﻿﻿Some medical researchers support a proposed mechanism by which smoking could cause lung cancer.  
 Okay, great. So there's a proposed mechanism, meaning that there's some  theoretical  way smoking could cause lung cancer. Is there any evidence to support that the proposed mechanism is, you know, correct?

We don't know. We know that "some" researchers support the "proposed" mechanism, but have no idea whether it's actually correct. So this statement is insufficient, too.

Taken together, all we have is a correlation -- which isn't causation -- and a theoretical mechanism, which isn't actual evidence. So even together, the statements are not sufficient. The answer is (E).

I hope that helps!  
 
​I feel like, from reading the explanation of statement 1 from Official Explanation, "But correlation evidence, by itself, provides no proof of a causal relationship", I can conclude that statement 1 helps answer the question: No, since this is a correlation, then it is NOT a causation. Right?

pierjoejoe · Answer

A CAUSAL RELATIONSHIP

(1) tells us that researchers show CORRELATION, NOT CAUSATION.

in general CAUSATION != CORRELATION
in any case it also says that research "consistently shows" --> it does not mean there is any proof for the correlation. the question is asking if there is a causa relationship, this statement does NOT tell us anything about any possible causal relationship.

(2) tells us that there are some researchers who support a theory on the mechanism that CAUSES the lung cancer --> but it specifically says "SOME MEDICAL RESEARCHERS" meaning that there is no real agreement about the mechanism and thus not real agreement on the cause of the cancer. the question is asking for the CAUSAL RELATIONSHIP --> thus we cannot conclude if there is or not a causal relationship (NOT SUFFICIENT)

(1)(2) there is correlation (statement 1) and a possible causation (statement 2). it is not sufficient to say BEYOND EVERY DOUBT that there is CAUSATION

Gaurav07 · Answer

Exactly my point. By casual is it trying to say 'Not very strong'? If it's not very strong, the statement A gives us a clear NO. However, statement B gives us a clear YES, since it mentions, some researchers, so it could be. It does indicate a casual relationship betwenn the two.

That's why I chose D.

Wazzzaa · Answer

Thanks for your answer.

I have understood your solution. I have I doubt.

What if the second statement is telling about results from a research :-

(2) ﻿﻿﻿﻿Some medical "researches" support a proposed mechanism by which smoking could cause lung cancer.

Then will the answer be: (B) ?

agrasan · Answer

Hi experts  KarishmaB   MartyMurray   IanStewart

(2) Some medical researchers support a proposed mechanism by which smoking could cause lung cancer.

Can we say that (2) is insufficient as it uses  "could"  which is just a possibility (not a certainty) whereas the main argument asks for kind of a certain evidence for a causal relationship between smoking and cancer?

Please let me know if my reasoning is wrong somewhere.

MartyMurray · Answer

Yes, the use of "could" is one clue indicating that statement (2) is not sufficient to confirm the answer to the question.

At the same time, the fact that statement (2) uses "could" is just a small part of why it's not sufficient. I think it's important to notice that, as a whole, statement (2) does not mean that smoking causes lung cancer because all it means is that some people believe that there's a good chance that smoking causes lung cancer by means of a certain mechanism. The fact that some people believe that doesn't mean what they believe is correct.

In general, it's better to decide that a statement is insufficient on the basis of the entirety of what it conveys than on the basis of the presence of just one word.

egmat · Answer

Let's tackle this interesting Data Sufficiency question about causation versus correlation - a concept that trips up many students. You're dealing with a yes/no question here: "Is there a causal relationship between smoking and lung cancer?"

Understanding What We Need 
To answer this definitively, you need to be able to say either YES (smoking causes lung cancer) or NO (it doesn't). Here's the key insight:  correlation does not equal causation . Just because two things occur together doesn't mean one causes the other.

Statement 1 Analysis 
"Research consistently shows a strong correlation..."

Think about this scenario: What if there's a genetic factor that makes people both more likely to smoke AND more susceptible to lung cancer? The correlation would exist, but smoking wouldn't be causing the cancer - the genetic factor would be the real culprit.

Since we can't distinguish between true causation and other explanations, Statement 1 alone is  NOT sufficient .

Statement 2 Analysis  
"Some medical researchers support a proposed mechanism..."

Notice those careful words: "some" researchers, "proposed" mechanism, smoking "could" cause cancer. This is just a theory with partial support - not proven fact. Without knowing if this mechanism is actually correct or widely accepted, you can't definitively answer yes or no.

Statement 2 alone is  NOT sufficient .

Combining Both Statements 
Even together, what do you have?
- A correlation (from Statement 1)
- A possible but unproven explanation (from Statement 2)

You still can't rule out alternative explanations like the genetic factor scenario I mentioned. The proposed mechanism remains just that - proposed, not proven.

Answer: E  - Both statements together are still not sufficient.

You can check out the  step-by-step solution on Neuron by e-GMAT  to master the systematic framework for distinguishing correlation from causation in DS questions. You'll also learn the three essential criteria for proving causation and how to apply them to similar problems. Feel free to explore other GMAT official questions with detailed solutions on Neuron for structured practice  here .

Is there a causal relationship between smoking and lung cancer?

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Is there a causal relationship between smoking and lung cancer?

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