Logical Reasoning

PT119 · S2 · Q22 Detective: Laser-printer drums are

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Detective: Laser-printer drums are easily damaged, and any nick in a drum will produce a blemish of similar dimensions on each page produced by that printer.

Conclusion (So)

We can reliably trace a document back to its specific printer by matching a blemish on the page with a nick on a drum from the printer.

Evidence

Any nick in a drum will produce a similar blemish on each page printed by that printer.

Evaluate

We could apply a Plan / Goal template to thinking about this.

GOAL: trace a printed document back to the precise printer it was printed on PLAN: match up a blemish on the print to a nick on the drum of a printer

To weaken, we want to think,

How would we match a blemish on a page to the nick of a drum on a printer, but FAIL to have traced that print back to the printer it came from?

Maybe more than one printer would have a nick that would match our blemish?

Goal

Identify an answer that demonstrates potential flaws in the method of matching blemishes to printer nicks, challenging the assertion that this reliably indicates the specific source printer.

22.

Which one of the following, if true, most weakens the detective's argument?

  1. Criminals are unlikely to use

    No Impact

    This choice discusses the likelihood of a criminal using their own printer, which is irrelevant to the reliability of matching blemishes to nicks and determining the specific printer source.

    4% picked this

  2. Drum nicks are usually so

    No Impact

    This mentions the skill required to determine the size and shape of a blemish but doesn't directly undermine the reliability of tracing documents to specific printers once a match is made.

    3% picked this

  3. Correct

    The manufacturing process often produces

    Why this is right

    This suggests that the same nick may be produced on several different printers. Therefore, even if a blemish is matched to a nick, multiple printers could have the same defect, casting doubt on whether we've identified the specific printer source, thereby undermining the reliability of the tracing method.

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

    77% picked this

  4. Blemishes on documents are sometimes

    Weaker Impact

    This indicates that blemishes might be totally concealed, but the argument relies on cases where blemishes are found and matched, so it hardly impacts the core claim about tracing printers. If blemishes were always concealed, then the Plan wouldn't be feasible. But sometimes just means "at least once".

    11% picked this

  5. Most suspicious documents are not

    No Impact

    This notes that suspicious documents are usually not on laser printers, which is unrelated to whether the blemish-matching method reliably works for those that are on laser printers.

    6% picked this

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