8.4 Evaluating Arguments: Assumptions, Flaws, and Support

8.4 Evaluating Arguments: Assumptions, Flaws, and Support

Quick Summary: The third task OPM names for the Occupational Reasoning Assessment is evaluate arguments. These items present a short piece of reasoning and ask what it assumes, what is wrong with it, or what would make it stronger or weaker. Unlike Section 8.2, where conclusions follow with certainty, arguments here are typically probabilistic — the question is whether the evidence adequately supports the conclusion.

Step one: separate conclusion from evidence

Before evaluating anything, identify the two parts.

• The conclusion is what the argument wants you to accept.
• The evidence is what it offers in support.

Signal words help. Therefore, so, thus, it follows that, clearly introduce conclusions. Because, since, given that, as shown by introduce evidence.

"Processing times fell after the new intake system was introduced. The new system must therefore be more efficient than the old one."

Conclusion: the new system is more efficient. Evidence: processing times fell after it was introduced.

Writing these on two lines makes the gap between them visible, and the gap is where the item lives.

Assumptions

An assumption is an unstated premise the argument needs in order to work. The test is simple: if this were false, would the argument collapse?

In the example, the argument assumes nothing else explains the fall — no staffing increase, no drop in the number of requests, no change in what counts as processing. If any of those did explain it, the conclusion no longer follows.

The negation test

To check whether a stated option is a necessary assumption, negate it and see whether the argument still stands.

• Candidate assumption: No other change occurred that could have reduced processing times.
• Negated: Another change occurred that could have reduced processing times.
• Does the argument still work? No. So it is a necessary assumption. ✓

Contrast with:

• Candidate assumption: The new system was expensive to install.
• Negated: The new system was inexpensive.
• Does the argument still work? Yes — cost is irrelevant to efficiency. So this is not an assumption. ✗

The three flaws that appear most

1. Correlation treated as causation

Two things occur together, or one after the other, and the argument concludes one caused the other. This is the same error covered in Section 4.3, and it is the single most common flaw in argument items.

"Units that hold weekly meetings have lower error rates. Weekly meetings therefore reduce errors."

Alternative explanations abound: well-managed units might both hold meetings and have low error rates, with management quality causing both. Or units with low error rates may have more time available for meetings — reversing the direction.

Whenever an argument moves from associated with to causes, ask three questions: could something else cause both? Could the direction be reversed? Could it be coincidence?

2. Unrepresentative sample

A conclusion about a whole group is drawn from evidence about a part that may not represent it.

"A survey of staff who attended the optional training rated it highly. The training is therefore valued across the unit."

Those who chose to attend are not representative of the unit. People who expected to find it useful selected themselves into the sample.

Watch for evidence drawn from volunteers, from one office generalised to all offices, or from one period generalised to all periods.

3. Overlooked alternative

The argument treats one explanation as established without ruling out others.

"Complaints dropped after the new form was introduced, so the form is clearer."

Perhaps the complaints channel changed. Perhaps fewer people applied. Perhaps complaints moved elsewhere.

Strengthen and weaken

These items do not ask you to prove or disprove. They ask which option most increases or decreases the likelihood that the conclusion follows.

Argument: processing times fell after the new intake system, so the system is more efficient.

Strengthens: staffing levels and request volumes were unchanged throughout the period. Weakens: the unit added four staff in the same month the system launched. Neither: the system cost $40,000. (Irrelevant to efficiency.)

The irrelevant option is always present, and it usually mentions something concrete from the argument, which is what makes it look responsive.

Guarding against your own views

A distinctive hazard: evaluating whether the conclusion is true rather than whether the argument supports it. A conclusion can be correct while the reasoning offered for it is poor, and an argument can be well-constructed while reaching a conclusion you find implausible. These items assess the reasoning.

This connects back to the closed-text principle. The task is to evaluate what is on the page, not to consult your own knowledge of federal administration.

Procedure

1. Underline the conclusion; bracket the evidence.
2. State the gap between them in one sentence.
3. Ask what must be true for the evidence to support the conclusion — that is the assumption.
4. Check for the three common flaws.
5. Match the option to the question asked: assumption, flaw, strengthen, or weaken.