Summary
Any female wood duck will lay an egg in the nest of another female wood duck if she sees the other duck leave her nest. Under natural nesting conditions, this behavior is rare because wood duck nests are usually well hidden. However, nesting boxes put up by people undercut the wood duck’s reproductive efforts. Why? Because the nesting boxes become so crowded with eggs that few of them will ever hatch.
Strongly Supported Conclusions
If the nesting boxes put up by people were better hidden, then the boxes would be more successful in aiding the wood duck’s reproductive efforts.
A
Female wood ducks will establish nests in nest boxes only when natural nesting sites are not available.
We don’t know what causes a female wood duck to establish a nest in a nesting box. We only know that female wood ducks will lay eggs in another duck’s nest if she sees that duck leave the nest.
B
Nesting female wood ducks who often see other female wood ducks are the most successful in their breeding efforts.
We don’t know which female wood ducks reproduce most successfully.
C
The nesting boxes for wood ducks have less space for eggs than do natural nesting sites.
We don’t know whether the nesting boxes have less space. We only know that the nesting boxes tend to be overcrowded, but that does not imply that these nesting sights are smaller than natural nesting sites.
D
The nesting boxes would be more effective in helping wood ducks breed if they were less visible to other wood ducks than they currently are.
The argument concludes that the nesting boxes undercut the duck’s reproductive efforts because the boxes become overcrowded. If the cause for overcrowding the nests were reduced, then the effect of undermining reproductive efforts would also be reduced.
E
Nesting boxes are needed to supplement the natural nesting sites of wood ducks because of the destruction of much of the ducks’ habitat.
We don’t know whether the nesting boxes are needed, and we don’t know whether the wood ducks’ habitat is being destroyed.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that owning a VCR prompts people to go to the movie theater more. She bases this on a correlation: people who tend to go to the movies more often also own a VCR.
Identify and Describe Flaw
This is a cookie-cutter “correlation does not imply causation” flaw, where the author sees a positive correlation and jumps to the conclusion that one thing causes the other, without ruling out alternative hypotheses. Specifically, she overlooks two key alternatives:
(1) The causal relationship could be reversed—maybe going to movies more causes people to get VCRs, not the other way around.
(2) Some other, underlying factor could be causing the correlation—maybe there’s something that causes people to both go to the movies and buy VCRs. (Maybe they simply like movies in general?)
A
concludes that a claim must be false because of the mere absence of evidence in its favor
The author doesn’t bring up a lack of evidence for any claims. Rather, she reaches her conclusion by presenting evidence in the form of a correlation.
B
cites, in support of the conclusion, evidence that is inconsistent with other information that is provided
The only evidence cited is a correlation between people who own VCRs and people who go to the movies more often. Everything else in the stimulus is at least consistent with this correlation being true.
C
fails to establish that the phenomena interpreted as cause and effect are not both direct effects of some other factor
This describes a key alternative hypothesis that the author ignores. She fails to establish that VCR ownership and moviegoing are not both direct effects of some other, underlying causal factor. (Maybe they’re both effects of simply liking movies in general?)
D
takes a condition that by itself guarantees the occurrence of a certain phenomenon to be a condition that therefore must be met for that phenomenon to occur
This is the cookie-cutter flaw of mistaking a sufficient condition for a necessary one. The author doesn’t make this mistake, and her argument doesn’t rely on conditional reasoning. Instead, she uses causal reasoning (and overlooks possible alternative hypotheses in the process).
E
bases a broad claim about the behavior of people in general on a comparison between two groups of people that together include only a small proportion of people overall
This is the cookie-cutter flaw of overgeneralization. But the author doesn’t generalize from a limited sample to an overly broad conclusion. Rather, she compares all people who own VCRs to all people who don’t, and so considers all people overall.