Flawed Parallel Reasoning Questions - - Question 26
In yesterday's council election a majority of voters supported conservative candidates, and a majority of voters supp...
Replies
Anita May 8, 2018
From the stimulus, what we hear is that most voters went conservative, and most went anti-pollution. The conclusion is that most voted for anti-pollution conservatives. But perhaps the people elected were mostly - (C for conservative, L for liberal/A for anti-pollution, P for not)CP CP CP CA LA LA LA
It's then true that most were conservatives and most were anti-pollution, but really only one was conservative and anti-pollution. We're looking for the match.
B tells us something similar. (P = like pies, B = like blueberries)
P P P BP B B B
Perhaps only one child out there is really like a blueberry pie and all others are either like blueberries or pies.
D goes in a different direction. It tells us the majority of customers who come to the restaurant always get fish & stuffed mushrooms, so they must be the most popular dishes. We do know that at least a majority of people get them, but there's also the potential that everyone, not just a majority, who goes also orders the chips and salsa to start with, so really, that's the most popular dish. This is a flaw, but a very different one. The problem isn't so much about conflating two different majorities into one, cohesive one, but about extrapolating from incomplete evidence.
Does that help?
Ashley-Tien July 8, 2018
Is there a name for the flaw? I thought the stimulus was incorrectly assuming that there would be overlap between conservatives and anti-pollution candidates
Christopher July 30, 2018
@Ashley-Tien, I don't know the name of the fallacy off the top of my head, but you're right that the problem is that is assumes too much of an overlap. There will be SOME overlap because both statements refer to a majority. The flaw is in assuming that two majorities within the same group of people represent exactly the same people. There will necessarily be some overlap, but that doesn't mean that every person from each majority is a member of the other majority.