9.3 Critical Reasoning & Decision Rules

Judging Arguments and Deciding by the Rules

The final strand of analytical ability asks you to reason critically: pick the strongest argument, decide who qualifies under a stated rule, separate cause from coincidence, and ignore facts that do not matter. Every argument has two parts - premises (the support) and a conclusion (the claim). Your task is not to agree or disagree personally but to judge whether the reasoning holds and which option best answers the exact question.

Assumptions, strengthening, and weakening

An assumption is an unstated premise the conclusion silently needs. To strengthen an argument, an option adds support or rules out an alternative; to weaken it, an option exposes a gap or offers a competing explanation.

Worked example. A report says, 'Crime dropped after more streetlights were installed; therefore streetlights reduce crime.' Which fact would most weaken it? 'A new police patrol program began at the same time as the streetlights' is strongest, because it supplies an alternative cause for the drop, so the lights may deserve no credit. Facts like 'the streetlights were energy-efficient LEDs' or 'residents liked the brighter streets' are irrelevant to whether crime actually fell.

Cause versus correlation (the post hoc trap)

A favorite CSE trap is assuming that because B happened after A, A caused B. A manager reasons, 'Attendance improved after we offered free coffee, so the coffee caused it.' The flaw is mistaking sequence for causation (the post hoc fallacy) - attendance might have risen because of a new bonus, better weather, or a looming deadline. Correlation is not causation. To justify a causal claim you must rule out other changes, show a plausible mechanism, and see the pattern repeat across cases.

Worked example - strengthening. 'Offices that adopted a queue-number system cut waiting time, so our office should adopt it.' The option that most strengthens the plan is 'Three offices similar in size and workload to ours cut waiting time by 30% after adopting the system' - it shows the result repeats in comparable settings. A weak option such as 'the system uses a modern touchscreen' names a feature, not an outcome.

Deciding under stated rules

Many items give you a rule and ask you to apply it exactly. Consider a scholarship whose applicant qualifies only if all three conditions are met: R1 a General Weighted Average (GWA) of at least 85; R2 annual family income of at most PHP 200,000; R3 enrolled full-time.

Only Aldo satisfies R1, R2, and R3. The discipline is that an 'all of the following' rule fails the moment one condition is missed - a 90 GWA cannot rescue Bea's over-limit income. When a rule uses 'or', by contrast, meeting any one condition is enough.

Necessary versus sufficient conditions

A subtle CSE distinction is between a necessary condition (required, but not enough on its own) and a sufficient condition (enough by itself). 'You must be 18 to take the CSE' is necessary - being 18 does not guarantee a passing rating, but you cannot sit the exam without it. 'Scoring 80.00 guarantees eligibility' is sufficient - reaching it settles the outcome. Watch for the reversal trap: from 'all passers scored at least 80' you may not conclude 'everyone who scored 80 passed on this attempt' unless the rule says the condition is both necessary and sufficient.

Spotting irrelevant information

Good decisions ignore facts that do not bear on the rule. In the scholarship above, an applicant's course, hometown, or age is irrelevant, because none appears in R1-R3. Suppose a fifth applicant, Elsa, has GWA 92, income 150,000, and full-time status, but the item adds that she 'lives four hours from the school'. Distance is not one of R1-R3, so it changes nothing: Elsa qualifies. Exam items often bury one useful number among several distractors; cross out anything the rule never mentions before you decide.

Choosing the strongest argument

The strongest argument is (1) directly relevant to the exact question, (2) based on fact or sound logic rather than emotion, and (3) complete, not dependent on an unstated leap. Weak arguments appeal to feelings ('everyone will be upset'), drift off-topic, or rest on unverifiable claims.

A structured decision approach

1. State the question precisely - what is being decided?
2. List the criteria and mark each as 'must' (AND) or 'any' (OR).
3. Screen each option against every criterion and eliminate on the first failure.
4. Discard irrelevant facts that no criterion mentions.
5. Pick the choice that is relevant, evidence-based, and complete.

Follow those five steps and critical-reasoning items - often the 'hard'-tagged questions - become a mechanical checklist rather than a matter of opinion.