Decision Making
What the section tests
Decision Making assesses logical reasoning, interpretation of data and arguments, and problem-solving under time pressure. Question families include syllogisms, Venn-diagram reasoning, ordering and seating puzzles, conditional logic, probabilistic reasoning, and evaluation of arguments (main conclusion, assumption, strengthening or weakening evidence).
Concepts to master
Know the quantifiers: all, some, none, most. 'Some' means at least one and possibly all; it does not mean 'some but not all'. For conditionals, 'If A then B' permits B without A and forbids A without B; the valid inference is the contrapositive, 'If not B then not A'. For puzzles, build a compact grid or list and apply constraints one at a time. For arguments, separate the conclusion from the evidence and ask what must be assumed for the evidence to support it.
Traps
Reversing a conditional, treating correlation as causation, and adding information not given are frequent. In Venn questions, do not assume that overlapping categories must overlap in the way a simple diagram suggests; test the minimum-overlap case. In probability, check whether events are independent and whether items are replaced.
Worked example
'All doctors are graduates. Some graduates are cyclists.' Does 'some doctors are cyclists' follow? No. The cyclists may all be graduates who are not doctors. A valid conclusion is only that some cyclists are graduates (if any cyclists exist). Rule of thumb: if you can draw a consistent diagram in which the conclusion is false, it does not follow.