PrepTest 147, Section 4, Question 25
One way to compare chess-playing programs is to(62 more words not shown)
Which one of the following(8 more words not shown)
- AIf one chess-playing(36 more words not shown)
- BHow fast a(16 more words not shown)
- CIn general, the(24 more words not shown)
- DIf two different(34 more words not shown)
- EIf a chess-playing(40 more words not shown)
Reading the argument
More time to think could help a chess program—but here both computers get the same time. The faster computer lets the same program examine more possibilities within that limit. Keep those conditions together: one program, two compatible computers, and a fixed amount of time per move.
What we’re looking for
The explanation makes sense if looking at more moves improves the program's chances. Compare examining one possible move with examining a hundred: the larger search could uncover a useful move the smaller search misses. That doesn't mean the program must win, just that it has a better chance. For this most-strongly-supported question, I'd look for that connection between examining more possibilities and a greater chance of winning.
Working the answers
- A
This compares two different programs running on the same computer. The passage compares the same program running on different computers. Different programs might differ in how well they evaluate the moves they examine, so examining more moves needn't settle which program is better. We can't carry the same-program comparison over to this changed situation without more information.
- B
The passage starts with computers on which the program is compatible. It doesn't explain what makes a computer compatible. Perhaps a program requires a minimum speed, or perhaps speed has nothing to do with compatibility. Neither possibility is settled by comparing performance after compatibility is already assumed.
- CCorrect
This states the connection the passage uses to explain its result: the same program gets a better chance of winning when it can examine more moves within the given time. The claim concerns improved chances, not a guaranteed victory. It also keeps the program fixed instead of comparing how two different programs think.
- D
Both the program and the computer change here. A faster computer gives a particular compatible program more opportunities within the time limit, but we aren't told that it must let one program examine more moves than an entirely different program on another machine. Differences between the programs could affect how much work each does.
- E
Giving the slower computer more time might help, but how much more? A tiny increase might not make up for the speed difference; a large increase might more than make up for it. The passage's comparison holds time fixed and doesn't tell us what extra allowance would equalize performance. Simply saying 'more time' doesn't establish an equal chance of winning.
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