Decision Making Flashcards

A Venn diagram shows: Group X only = 8, Group Y only = 12, Both = 5, Neither = 3. How many people are in the survey?

Answer: 28

Total = 8 + 12 + 5 + 3 = 28.

'Either the project finishes on time or we lose the contract. The project finished on time.' What follows?

Answer: The contract is not necessarily saved — other conditions may apply

The 'either…or' is stated as a sufficient condition for one outcome, but we are not told it is the only condition for keeping the contract. We cannot conclude with certainty.

If P → Q and Q → R, and P is true, what is true?

Answer: R is true

Hypothetical syllogism: P → Q, Q → R, P is true → Q is true → R is true. This is a transitive chain.

A car depreciates by 20% per year. It costs £25,000 new. What is it worth after 2 years?

Answer: £16,000

After year 1: £25,000 × 0.8 = £20,000. After year 2: £20,000 × 0.8 = £16,000. Compound depreciation, not simple.

A scheduling puzzle: A must happen before B. C must happen before A. D must happen after B. What is a valid order?

Answer: C, A, B, D

Constraints: C < A < B < D. Only C, A, B, D satisfies all three ordering rules.

In a group of 100 patients, 60 were given a treatment. Of those, 45 improved. Of the 40 untreated, 20 improved. What is the relative risk of improvement with treatment?

Answer: 1.5

Risk with treatment = 45/60 = 0.75. Risk without = 20/40 = 0.5. Relative risk = 0.75/0.5 = 1.5.