Q8 - Of 2,500 people who survived

[b91302310]

The correct answer is (E).

Is it correct because the evidence only mentions people who "survived" the first heart attack, whereas the conclusion includes people "have" heart attack, which is broader than the scope of evidence? So,the argument could be fixed by providing data on people who did not survive a first heart attack.


Thanks.

[aileenann]

Yup - you are absolutely right. From data about people who survived a first heart attack, we can't draw conclusions about when either nonsmokers or smokers tend to have their first heart attack. To draw such a conclusion we would have to have information about when each group has its first heart attacks.

[redcobra21]

If the stimulus had accounted for people who had not survived a first heart attack, would this conclusion have been valid? I find it hard to accept that such a conclusion could be drawn by simply taking the difference between two medians. What would an answer choice have looked like if it was attacking the stimulus from this angle? I think that's why I was thrown a bit off by (D) - it seemed to be suggesting that the median might not actually reflect a general tendency (for example, if 49 people received their first heart attack at 26, 49 received it at 80, but the two who accounted for the median received it at 51, then wouldn't that undermine the conclusion?)

[WaltGrace1983]

If the stimulus had accounted for people who had not survived a first heart attack, would this conclusion have been valid? I find it hard to accept that such a conclusion could be drawn by simply taking the difference between two medians. What would an answer choice have looked like if it was attacking the stimulus from this angle? I think that's why I was thrown a bit off by (D) - it seemed to be suggesting that the median might not actually reflect a general tendency (for example, if 49 people received their first heart attack at 26, 49 received it at 80, but the two who accounted for the median received it at 51, then wouldn't that undermine the conclusion?)

I like where your head's at. Let me explain.

Let's say the argument looked more like this: "Of 2,500 who had a first heart attack, those who did not smoke had it at a median age of 62 while those that did smoke had it at a median age of 51. On this basis of this information, nonsmokers tend to have a first heart attack eleven years later than do people who smoke."

I think one thing that is super important (and someone please correct me if I am wrong) is that the argument is solely talking about the study described. It says "from the basis of this information," thereby showing that this information is all we are basing it off of. From this angle, I don't see any problems. I think your argument would be much stronger if the conclusion said something along the lines of "thus we can conclude that people generally have heart attacks..." This conclusion would turn this stimulus into a very simple flaw problem that makes one small sampling representative of an entire population.

[Abeckham13]

Why do Deaths in this case actually matter? All that matter is when they had their heart attack. Whatever or not they live or die seems completely irrelevant.

[WaltGrace1983]

Why do Deaths in this case actually matter? All that matter is when they had their heart attack. Whatever or not they live or die seems completely irrelevant.

You just committed the same flaw that the test did Read this question again. We are given two pieces of information and then a conclusion is drawn based on these two pieces.

Of the 2,500 that survived a first heart attack, those that didn't smoke had it at age 62
+
Of the 2,500 people that smoked, they had their first heart attack at age 51
→
Nonsmokers tend to have first heart attack 11 years later

So we are given a piece of information about (1) nonsmokers and (2) smokers. Look at this information though, does it lead to the conclusion? Not necessarily! Why? Because we are merely talking about the nonsmokers that survived their first heart attack. What if most people don't survive their first heart attack?

The conclusion is thus making a comparison between apples and oranges. The first piece of information is talking about people that survive while the second piece of information - the second premise - is talking about people that simply had their first heart attack. Do you see the difference?

How could we correct this?

We would correct it by comparing apples to apples or oranges to oranges. Let me explain...

Of the 2,500 that had a first heart attack, those that didn't smoke had it at age 62
+
Of the 2,500 people that smoked, they had their first heart attack at age 51
→
Nonsmokers tend to have first heart attack 11 years later

[ltownsjr]

I think the big thing here is how to recognize quickly that the flaw comes from the first premise and not the second in my opinion...if someone knows a key to figuring that out, it would be much obliged lol.

[seychelles1718]

0

[kkmoslehpour]

I agree with dypark92, it seems like the premise is simply saying: There are 2500 people that survived, and out of the survived 2500 people there are non-smokers and smokers. The reason I say this is because they said, of "those" 2500 people [that survived], people who smoked had their first heart attack at 51. So please correct me if I am wrong. I don't get why the answer choice is E, why do we care about the people that did not survive? We are simply comparing people that DID survive. Is it because the conclusion generalizes the fact of non-smoker and smokers when the premise only talks about "survived" smokers and non-smokers, therefore we need more data on the "non-survivers" to close this gap?.

[hnadgauda]

I still don't understand why data on people who didn't survive their first heart attacks is important.

The stimulus looks at 2500 people who survived a 1st heart attack. Those who didn't smoke had their 1st heart attack at a median age of 62. Those who smoked 2 packs of cigarettes a day had their 1st heart attacks at a median age of 51.

I don't see how the conclusion of nonsmokers having their 1st heart attack 11 years later than people who smoke 1 packs of cigarettes a day, is wrong. Can someone please clarify?

[ohthatpatrick]

If we wanted to compare the age of smokers' 1st attack to nonsmokers' 1st, we would need to know when everyone's 1st heart attack was.

But we're only asking people who SURVIVED a 1st heart attack.
We also need the data on people who DIED during their 1st (and only) heart attack.

Consider a smaller (manageable) data set of 5 people each:

Age of 1st attack for nonsmoker survivors
(50, 61, 62, 64, 67) - median age of 62

Age of 1st attack for smoker survivors
(48, 49, 51, 53, 58) - median age of 51

Now consider we consider the ages of people who DIED during their 1st attack.

Age of 1st for nonsmokers who died during attack
(39, 42, 44, 47, 49)

Age of 1st for smokers who died during attack
(45, 49, 56, 60, 61)

When you combine those data sets, you get

AGE OF 1ST ATTACK FOR NONSMOKERS
(39, 42, 44, 47, 49, 50, 61, 62, 64, 67) - median age of 49.5

AGE OF 1ST ATTACK FOR SMOKERS
(45, 48, 49, 49, 51, 53, 56, 58, 60, 61) - median age of 52

With this data, nonsmokers DO NOT tend to have their 1st attack eleven years later.

Obviously I created my own data for the 1st attack for dead smokers/nonsmokers, but the point of (E) is that the missing data could actually make the conclusion dead wrong (no pun intended).

Here's an analogous argument:
Of 2,500 people who were admitted to Harvard Law and made it to their third year, the boys had a median LSAT score of 168 and the girls had a median LSAT score of 173. Thus, girls who were admitted to Harvard Law tend to have an LSAT score that's five points higher than that of boys admitted to Harvard Law.

This conclusion is missing information about the median LSAT scores of boys/girls who were admitted to Harvard but dropped out during their first or second years.

[VendelaG465]

so whether they died or survived the point is that there is a whole other different group (those who had their first heart attack & died ) that wasn't accounted for in the study/data? so nonsmoker,smoker, & the group who died am I interpreting this correctly?

[ohthatpatrick]

Yeah, you've got it.

If we pose the question, "Who has their first heart attack earlier: smokers or nonsmokers?"

Then we would want to know
- on average, when was the first heart attack for smokers
- on average, when was the first hear attack for nonsmokers

Telling me that, on average, "Smokers who survived their first heart attack had it around age 60" is not enough data.
What about the "smokers who didn't survive their first heart attack"?

We need, for ALL smokers, when was their first heart attack.

Telling me about the 1st heart attack for the smokers who survived their first heart attack is only giving me part of the data I want.
I need to also know about the 1st heart attack for smokers who were killed by that heart attack in order to compute the average age that smokers have their first heart attack.

[VendelaG465]

thanks!