Quality control investigator

Answer choices

1. A

   Out of Scope10% picked this

   bases its conclusion on too small a sample of items tested

   Out of Scope: "too small a sample" We have no grounds for thinking the sample was too small. These samples were acquired from various manufacturing locations, so we can't even say, "Sure, Factory X has a 20% rate of defects, but all the other factories have a way lower rate".

   10%
2. B

   Too Strong: "just as likely"12% picked this

   presumes, without providing justification, that the field inspectors were just as likely to choose a defective item for testing as they were

   Is this author assuming that the field inspectors were just as likely to choose a defective item as they were a nondefective item? Close, but not quite. The author is assuming that the field inspectors were randomly choosing items as samples. But, if they were randomly choosing items, and the rate of defectiveness was 20% (1 out of 5), then they would be 4 times as likely (80%, 4 out of 5) to choose a nondefective item. So in the author's mind, where inspectors grabbed samples randomly, and 1 out of every 5 samples was defective, she would be assuming that the inspectors were less likely to choose a defective item than a nondefective item, since 4 out of those 5 times they grabbed a nondefective item.

   12%
3. C

   Doesn't Weaken12% picked this

   overlooks the possibility that a few of the manufacturing sites are responsible for most of

   This doesn't work as an objection. Even if a few sites are responsible for most defective items, the manufacturer is still averaging out to an unacceptable 20% defective rate. We would need to know that the "various manufacturing locations" from which the inspectors grabbed their samples just happened to disproportionately skew towards these few "bad apple" manufacturing sites. But since this answer doesn't give us a storyline like that, there's no way to argue that the 20% is a skewed number.

   12%
4. D

   Correct61% picked this

   overlooks the possibility that the field inspectors tend to choose items for testing that they

   Why this is right

   This does work as an objection. If the inspectors were trying to find items they assumed were defective, then they're not grabbing random samples, they're seeking out the ones that look bad. In that case, the samples that make it back to the lab are not a representative sample of the items being manufactured, they are a skewed sample. Thus, the author can't go from knowing that 20% of the samples are defective to thinking that 20% of the total items are defective.

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

   61%
5. E

   Too Strong: "equal number"5% picked this

   presumes, without providing justification, that the field inspectors made an equal number of visits to each of the various

   The author doesn't need to assume anything as specific and precise as "the inspectors made an identical number of visits to each site". The author is only assuming fuzzy ideas like, "the inspectors did not make a significantly greater number of visits to sites that were known to have higher rates of defective items".

   5%