Self-study
Support In the first decade following the founding of the British Labour party, the number of people regularly voting for Labour increased fivefold. ███ ██████ ██ █████████ ██████ ██████ █████████ █ ███████ ████████ ██████ ███ █████████ ██████ ███████ █████ ███ ████████ ███ ████ ███ ████ ██ ███ █████ ██ ██ ███ ██████ ███████ ███ ██████████ █████ ████ ███ ██████ █████ ██████ ████ ██████ ██ ███ █████████ ██████ ██████ ████ ██ ███ █████ ██ ███████ ██████
Argument Breakdown
The argument concludes that the British Labour party did not gain more voters in its second decade than in its first decade. This is supported by a sub-conclusion that Labour saw the same increase in both decades. In turn, the sub-conclusion is supported by data from those two decades: in the first decade, Labour saw a five-fold increase in voters. In the second decade, there was another five-fold increase in Labour voters.
Identify a Flaw: Numbers and Percentages
The argument's conclusion is about the number of voters Labour gained. But the sub-conclusion is about the percentage increase. Even though the percentage increase was the same, is it really supported that voters increased by the same number in each decade?
Each decade saw a five-fold increase: voters increased by a factor of five. But that's just a percentage increase, and doesn't tell us the amounts involved. Let's apply some actual numbers, assuming Labour started with 10 voters:
Decade 1: 10 voters x 5 = 50 voters (increase of 40)
Decade 2: 50 voters x 5 = 250 voters (increase of 200)
So even though Labour had the same percentage increase across each decade, it has a much greater numerical increase in the second decade—of course, because it started with more voters! That means not only is the conclusion unsupported; it actually must be false based on the argument's premises. That's the argument's flaw.
There are several ways this could be phrased—confusion between numbers and percentages, drawing a conclusion contradicted by the premises—but one way or another, this is the flaw the correct answer will describe.
19.
The reasoning in the argument ██ ██████ ███████ ███ ████████
a
fails to specify █████ █████████ ██ ████████ ███ █████ ██ ███ ███████████ ████ ██████ ███ ████████ ███████ ██ ██████████████ ███████ ███ ████ ███████
The argument doesn't need to specify dates, because it adequately distinguishes between the two decades in question. Whether Labour was founded 20 years ago or 200 years ago, it doesn't matter. The dates (A) mentions aren't necessary, or even useful to the argument.
b
draws a conclusion ████ ██████ ██ ████ ██ ███ ███ ████ ████████ ██ ███ ███████ ███ ████
(B) accurately describes the problem with the argument. The data given in support say that Labour saw a five-times increase in voters during each of its first two decades. If Labour started with 10 voters, that looks like this:
Decade 1: 10 voters x 5 = 50 voters (increase of 40)
Decade 2: 50 voters x 5 = 250 voters (increase of 200)
This makes the conclusion that Labour's did not gain more voters in its second decade impossible. Labour started its second decade with more voters, so another five-times increase means a five-times greater number of new voters!
c
relies on statistical ████████ █████ ████████ █████████ ██ ██████████ ██ ████████████ ███ ██████████ █████
The argument's conclusion is about the number of voters Labour gained in each of its first two decades, and so are the statistics it uses as support. The argument's support is relevant to its conclusion—the argument just badly misinterprets that relevant information to draw a false conclusion.
(C) would be correct if the argument relied on truly irrelevant statistics, such as the increase in Labour's voters during its tenth decade. That would truly have no bearing on how many voters it gained during its first two decades.
d
fails to allow ███ ███ ███████████ ████ ███ ██████ █████████ █████████ ██ ███ ██████ █████ ███████ ██████ ███ ██████ ██ ████████
The argument is purely about how many voters Labour gained in each of its first two decades. Why it gained those voters, or what its policies were, has nothing to do with the argument. Failing to consider irrelevant information isn't a flaw.
e
overlooks the possibility ████ ████ █████████ ████ ████ ██ ███ ██ ███ ███ ███████ ████ ████ ████ ██ ███ █████
It doesn't matter how many elections were held in each decade—whether it was two or 20, the question is just how many voters Labour started and ended each decade with. If one decade had more elections than the other, that wouldn't affect the change in Labour voters between the start and end of each decade. The argument overlooks this information, but overlooking irrelevant information isn't a flaw.