Critical Reasoning

A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.

Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?
(A) the percentage of thundershowers in Plainville that occur in the spring
(B) the percentage of spring rainfalls in Plainville that are thundershowers
(C) the percentage of thundershowers in Plainville that result from low-pressure systems
(D) whether low-pressure systems in other areas are associated with rainfall
(E) whether Plainville has more or fewer thundershowers each spring than do near by towns.

OA to follow.

A sounds like correct answer

I pick C, thunderstorms caused by lower pressure % might give the probability

i chose C.
A and B do not connect the probability of the LOW PRESSURE systems to thunderstorms. Statement C does that .

Would go with B .

All we need to evaluate the possibility that "Plainville will have a thundershower soon"..

Since this a question about probability , we need to provide a direct answer which is more related to the facts currently being cited in the stimulus.

We know low-pressure system is approacing and currently its spring .Also we are told that chances of thunderstorms are most likely to occur in spring.

So answer choice which hits more with more specfic timing by connecting most details given , shall hit more specfic answer to the point and shall be the best one .

(A) the percentage of thundershowers in Plainville that occur in the spring --->Curent time is approaching low-pressure system , so even though there are high chances of thunderstom in spring but even in this spring those high chances may fall under non rainful days. Here things would have been much better , had low-pressure connection been cited.If low-pressure connection would have been cited , then it would have been the very much the current time which is knocking.Current time is spring but even more specific input than that ( given in stimulus) is low-pressure system is approaching now

But still lets Hold on this choice and look forward to choose if there are anyone better.

(B) the percentage of spring rainfalls in Plainville that are thundershowers
--> Find it better then previous one . Because we are being very specfic to the approaching time here. The spring has high chances of rain as low-pressure correlation in the stimulus states. Low-pressure-system now-->Rainy spring now-->Now if thundershowers are most in this time then probality is really high . On the flip side if thundershowers are least in this regard then a very low probability . This choice makes the result sway from one extreme to another extreme by being very close to the specfic time. Here spring , low-pressure , rainful all conditions are tied to give more specfic idea of time.
So let drop my earlier choice A and hold this and move to C.

(C) the percentage of thundershowers in Plainville that result from low-pressure systems
-->Low-pressure and thundershowers may be high degree of correlation . Ok, but what if maximum low-pressures occured in non spring season then even a high probability of non-spring season doesnt help us evaluate . Here we are missing the current time which is spring .

So i keep B

D & E can be dropped easily as they are way out.

papgust wrote:A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.

Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?
(A) the percentage of thundershowers in Plainville that occur in the spring
(B) the percentage of spring rainfalls in Plainville that are thundershowers
(C) the percentage of thundershowers in Plainville that result from low-pressure systems
(D) whether low-pressure systems in other areas are associated with rainfall
(E) whether Plainville has more or fewer thundershowers each spring than do near by towns.

OA to follow.

B ?

Confused on this one but I would go with A

OA is B. Rohan, i still don't get the idea of why B is correct.

the only reason, I would choose B ...

A low-pressure weather system is approaching Plainville and there is 70% chance of rainfall (data given in the stimulus).

According to choice A, there could be 10% chance or 99% chance ... we do not have the data...

papgust wrote:OA is B. Rohan, i still don't get the idea of why B is correct.

Hi papgust,

Remember, the author has to prove EVERY idea in the conclusion. So, if there is an idea in the conclusion that is not in the evidence, then the author must be assuming something about that new idea. This is why a key Kaplan tactic in arguments is to look for an idea in the conclusion that was not in the evidence. Next, look for an idea in the evidence that is not in the conclusion. In other words, look for ideas (or terms) that are differentially present in the conclusion and evidence. Then, connect them. This remains the best way to identify an assumption (while denial test is the best way to verify an assumption.)

Let's apply it to this question:

A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.

Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?

So, the author is trying to conclude something about thundershowers while his evidence is about likelihood of rainfall. (In this particular question, the conclusion appears in the question stem).

Now, that we've identified the differential terms in conclusion and evidence, it is a trivial matter to identify the assumption. The author is assuming that rainfall is almost always associated with thundershowers. (Note: there are several ways of stating the assumption; the important thing is that you've hit on the right idea.)

Now, it is really easy to see why determining the percentage of spring rainfalls in Plainville that are thundershowers would be very useful in determining the probability that Plainville will have a thundershower soon. (ie, choice B).

Choose B.

______

Note: in relevant information" (or "evaluate the argument") questions, it is very helpful to to figure out the assumption. In fact, thinking about the author's central assumption is helpful in: assumption, stn/wkn, flaw, and relevant information questions. Thinking about assumption is definitely NOT the right thing to do in: inference and paradox questions.

Wow..Reading the explanations really motivates me to explore more about CR!!


Thanks TestLuv..

I think the answer is more direct if we think mathematically...

A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.

F1: Low pressure systems cause 70% of rainfall in Painville.
F2: Low pressure systems can also cause thundershowers.
F3: In Current Season, Spring, thunderstorm are most likely to occur. ( most likely --> High Probability )

Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?
OR
Probability of thundershower in Spring?
OR
( Total number of thundershowers in Spring)/ (Total number of rainfall in Spring)


(A) the percentage of thundershowers in Plainville that occur in the spring
==> Number of thundershowers in Spring/ Total number of rainfall in Plainville.
(B) the percentage of spring rainfalls in Plainville that are thundershowers
Exactly - this is what we want.
(C) the percentage of thundershowers in Plainville that result from low-pressure systems
Number of thundershowers from LPS/Total number of rainfall from LPS.
(D) whether low-pressure systems in other areas are associated with rainfall
(E) whether Plainville has more or fewer thundershowers each spring than do near by towns.

D and E can be easily eliminated.