Historians of North American architecture who have studied early nineteenth-century houses with wooden floors have observed that the boards used on the floors of bigger houses were generally much narrower than those used on the floors of smaller houses.
Conclusion
Narrow floorboards in early-19th-century houses were probably a status symbol designed to proclaim wealth.
Evidence
Bigger houses (built for richer people) had narrower boards; smaller houses (built for poorer people) had wider boards.
Evaluate
The most common argument pattern on Strengthen / Weaken is Explain Curious Fact, so when the first sentence provides a Correlation (ppl with trait 1 were more likely to have trait 2), we're likely to get a causal explanation as our conclusion.
CURIOUS FACT: why are these correlated? Bigger houses || narrow floorboards Smaller houses || wider wider floorboards
EXPLANATION: Since we know that bigger houses were generally owned by richer people, the author speculates that the rich people sought out the narrow floorboards as a status symbol to flaunt their wealth.
As always, with this template, we need to consider 1. alternate explanations for the curious fact maybe bigger houses are just usually built with narrow floorboards for some structural reason
2. how plausible is the author's explanation do narrow floorboards cost more? are they coveted by the lower classes? do rich houseguests comment appreciatively about how narrow the floorboards are?
Goal
Let's look for an answer that strengthens the plausibility of the story that narrow floorboards were a luxury item that rich people would buy to brag about their wealth, or for an answer that undermines a different explanation for why bigger houses had narrower floorboards.