Logical ReasoningDifficulty: Hard

PT147 S4 Q25 Explanation

One way to compare chess-playing

A free, expert breakdown of this official LSAT Logical Reasoning question.

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Stimulus

One way to compare chess-playing programs is to compare how they perform with fixed time limits per move. Given any two computers with which a chess-playing program is compatible, and given fixed time limits per move, such a program will have a better chance of winning on the faster computer. This examine more possible moves in the time allotted per move.

What this question is testing

Most Supported

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
25.

Which one of the following is most strongly supported by the

Answer choices

  1. Too Strong: will Unknown Comparison18% picked this

    If one chess-playing program can examine more possible moves than a different chess-playing program run on the same computer under the same time constraints

    While this answer seems reasonable, since it's reinforcing the "more moves examined = better chance of winning" connection, we don't know how to compare these two different programs. It's not like the passage told us that the only thing that affects chance of winning is number of possible moves examined in the time constraint. Two different chess-playing programs have been designed by two different (groups of) computer programmers. We have no idea what other aspects of designing a chess program are important. Maybe Eddie's chess program can consider more possible moves than Sharon's chess program, but Eddie didn't give good instructions to his chess-playing algorithm for what to make of all those possible moves considered. He might have better raw materials (more data for the computer to consider when selecting the next move) but less wisdom in terms of selecting the best move on the basis of that richer data. Since the program that considers more possible moves might be terrible when it comes to strategically picking the best of those possible moves, it might still be less likely to win than the other chess program. The correct answer is pretty similar to this one, but the correct answer hedges its prediction, making it safer language. It says "in general, the program considering more moves will have a better chance". This answer says, "the program considering more moves will have a better chance".

  2. Too Strong: has no effect2% picked this

    How fast a given computer is has no effect on which chess-playing computer programs can

    We have no support for this strong claim. There could easily be older computers with slow processing speeds that are too slow for certain chess programs to run on them. The author even seemed to allow for this possibility by saying, "Given any two computers with which a chess-playing program is compatible", implying that there may be some computers with which a given chess-playing program is not compatible.

  3. Correct54% picked this

    In general, the more moves a given chess-playing program is able to examine under given time constraints per move, the better the

    Why this is right

    This is reinforcing the Causal Difference-Maker we were given in the final sentence. When we test a given chess program on two different computers, the program on the faster computer is more likely to win simply because it can examine more possible moves in the allotted time. That allows us to say that, "in general (which is kind of like saying all other things being equal), more moves = better chance of winning". This generalization definitely ignores other potentially meaningful variables that would exist if one chess program were playing a different one, but it softened its prediction by saying "in general", so it will tolerate exceptions to this rule.

    Skill tested: Most Supported · how this choice captures the argument's function is the move to repeat next time.

  4. Unknown Comparison Too Strong: will24% picked this

    If two different chess-playing programs are running on two different computers under the same time constraints per move, the program running on the faster

    We weren't really given any way to judge a comparison between two different chess-playing programs. In this head-to-head between program A and program B, we can say that program B is running on the faster computer. Does that guarantee that program B will consider more possible moves in the allotted time? No, because we don't know about design differences between program A and program B. Perhaps program B was written with really inefficient coding, so it takes more processing time/energy for B to consider a possible move than it does for A to consider a move. Since the design of the program could have such a difference on the performance efficiency of the program, we can't automatically say that any chess program on a faster program will consider more moves than any chess program on a slower computer.

  5. Too Strong: equal2% picked this

    If a chess-playing program is run on two different computers and is allotted more time to examine possible moves when running on the slow

    There probably is some break even point, where you offset the superior computer speed of one computer with a smaller time limit per move, so that Program A is able to calculate the same number of possible moves whether it gets 5 seconds on the slower computer or 4 seconds on the faster computer. But the ratio of time limits would have to match the inverse ratio of computer processing speeds. This answer choice is not dialing in the mathematical specificity it would take to end up with an equal (i.e. identical) chance of winning. It's simply saying, "if you give the program on the slower computer more time to examine possible moves, it'll be equal chance". Maybe if we give it an extra 0.5 seconds it's not enough extra time to consider an equal number of possible moves. Maybe if we give it an extra 20 seconds, then the program on the slower computer is now considering way more possible moves.

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