LR Problem Set #5

[satipod]

Hi! I had a hard time with 2 of the questions on this set.

Could I have some help with numbers 501 and 524.

With 501, I'm having issues understanding the language of the credited answer. I chose A on that one.

With 524, I'm having issues with the diagram. Initially, I thought this was just a mistaken reversal but for some reason but ended up struggling with it. Could I ask for the conditional diagramming for this question?

Thank you!!

Thank you!!

[Nikki Siclunov]

Q. 501 has a stimulus that can be diagrammed as follows:

Premise: Hot Days Unsafe Smog

Premise: Hot Days East Wind

Conclusion: East Wind Unsafe Smog

Clearly, there is an error in the formal logic (we cannot combine two "some" statements to make an inference). Let' say there are 5 hot days in Hillview each week (M-F). It's possible that the smog is unsafe on Monday and Tuesday only, and that the wind blows from the east on Thursday and Friday only. Although it is possible that there be a day on which the "Unsafe Smog" and "East Wind" overlap, the two sets could have nothing in common (even though they are all Hot Days). This error is described in answer choice (B).

Formal Logic is explained as a Virtual Module in Lesson 8 (accessible through the Online Student Center if you are enrolled in a full-length course).

Answer choice (A) describes a conditional error. Even if "Hot Days" were a condition that necessarily accompanies "Unsafe Smog," that would not produce the conclusion claimed in the argument:

Unsafe Smog Hot Days East Wind

Since this logical chain cannot produce an inference of the type specified in the stimulus, it does not describe a mistake made by the author.

[Nikki Siclunov]

Q. 524 also contains Formal Logic:

Premise: Political Action Social Justice

Conclusion: Social Justice NOT Political Action

Even if only a few of those who engage in political action do so out of a sense of social justice, it is possible that everyone who has a sense of social justice engages in political action.

Again, to master Formal Logic I recommend listening to the virtual module in Lesson 8, and then complete the drills in the pdf file that accompanies the module.

[satipod]

Thank you so much for that. Looks like I'll definitely have to delve into formal logic- I have kind of been avoiding it up until this point but it might just be the time to face it!

I also wanted to ask about #540 on that same set. I basically narrowed this down to A and B and couldn't decide between the two for the longest time. What exactly is it that renders B the better choice? I chose this answer ultimately, but I was really conflicted between the sample size option and the credited response.

Many thanks!!

[Nikki Siclunov]

The reason why (A) is wrong has to do with the conclusion of the argument: despite their similar physical form, guinea pigs stem from a separate ancestor. The author does not make a claim about rodents in general, and so the small sample size does not matter. Both the premise and the conclusion deal with a select number of individual species.

Answer choice (B), on the other hand, shows that the genetic differences between guinea pigs and mice do not, by themselves, establish that they stem from separate ancestors. Why? Because some pairs of species not having a common ancestor are more similar to each other than some pairs that do. If so, genetic differences alone would not prove the presence (or the absence) of a common ancestor.

Hope this helps!