Free Critical Thinking MCQs with Answers

1. All doctors in the hospital attended the seminar. Dr Ahsan did not attend the seminar. Which conclusion follows?

• A. Dr Ahsan is not a doctor in that hospital
• B. Dr Ahsan was ill
• C. The seminar was not important
• D. Dr Ahsan is a doctor elsewhere

Explanation: If every doctor in the hospital attended, then anyone who did not attend cannot be a doctor in that hospital, which is a valid contrapositive. The other options add information the statements never supply, such as a reason for the absence. A conclusion must follow necessarily, not merely plausibly.

2. Argument: "Students who take extra classes score higher, so extra classes cause higher scores." The main weakness of this argument is that it

• A. uses too small a sample
• B. confuses correlation with causation, ignoring that motivated students may both take extra classes and study more
• C. relies on an outdated study
• D. contradicts itself

Explanation: Two things occurring together does not establish that one produces the other, since a third factor such as motivation could produce both. Ruling this out would need a comparison of similar students assigned to classes or not. Correlation and causation is the most heavily tested flaw in critical reasoning sections.

3. Statement: "Every time I wash my car, it rains." This reasoning is flawed because it

• A. assumes a causal link between unrelated events, ignoring the times it rained without washing
• B. uses an unreliable weather forecast
• C. contains a contradiction
• D. generalises from an authority

Explanation: The speaker notices only the cases that fit the pattern and overlooks the many occasions when it rained without a wash or a wash was followed by sunshine. This selective attention is confirmation bias. A fair test would count all four possible combinations of the two events.

4. Which of the following, if true, would most weaken the argument that a new drug is effective because patients improved after taking it?

• A. The drug is expensive to manufacture
• B. A group given a placebo improved by the same amount
• C. The drug has been approved in other countries
• D. Some patients disliked the taste

Explanation: If untreated patients improved equally, the improvement cannot be attributed to the drug, which is precisely why controlled trials use a placebo group. Cost, taste and foreign approval say nothing about whether the drug works. A weakening statement must attack the link between the evidence and the conclusion.

5. Which of the following, if true, would most strengthen the claim that a city's new bus lanes reduced traffic congestion?

• A. The lanes were expensive to build
• B. Congestion fell in the city while remaining unchanged in comparable cities without bus lanes
• C. Many residents say they like the lanes
• D. Bus ridership figures were not recorded

Explanation: A comparison with similar cities that did not change rules out general causes such as fuel prices or the economy, which makes the link to the bus lanes far more credible. Opinions and costs are not evidence about congestion. Missing data weakens rather than strengthens a claim.

6. Identify the assumption: "We should build a new hospital because the population of the district has doubled."

• A. The existing health facilities cannot adequately serve the larger population
• B. The district has no hospitals at present
• C. Population growth will continue
• D. Hospitals are the cheapest form of healthcare

Explanation: The argument only works if current capacity is now insufficient, since a doubled population served by ample existing facilities would need nothing new. That unstated link is the assumption. The other options are neither required by the argument nor implied by it.

7. Statement: "Either we cut the budget or the project fails." This reasoning may be flawed because it

• A. presents a false dilemma, ignoring other possible options such as raising funds
• B. uses emotional language
• C. appeals to authority
• D. repeats itself

Explanation: A false dilemma presents two alternatives as though they were the only ones available, when in reality further options exist, such as extra funding, a revised timeline or a reduced scope. Recognising the unstated third possibility is the standard response. The flaw is also called the either or fallacy.

8. "Professor Khan says the treatment works, and he is a famous surgeon, so it must work." This argument relies on

• A. statistical evidence
• B. an appeal to authority rather than to evidence
• C. a controlled experiment
• D. a personal attack

Explanation: Expertise makes a claim worth listening to but does not by itself make it true, and the argument offers no data at all. An appeal to authority becomes especially weak when the authority speaks outside their field or when experts disagree. Attacking the person instead would be the opposite fallacy, ad hominem.

9. "You cannot trust his views on pollution because he drives a large car." This is an example of

• A. an ad hominem attack
• B. a false dilemma
• C. a hasty generalisation
• D. circular reasoning

Explanation: The argument attacks the person's behaviour rather than examining the merits of what he says, and inconsistency in a speaker does not make their claim false. This particular version is sometimes called tu quoque. The claim about pollution must be assessed on its own evidence.

10. "This medicine is safe because it is natural." The flaw in this argument is that it

• A. assumes that being natural guarantees safety, which many natural poisons disprove
• B. uses an unreliable source
• C. is circular
• D. attacks the manufacturer

Explanation: Snake venom, arsenic and deadly nightshade are all entirely natural, so the premise does not support the conclusion. This is the appeal to nature fallacy. Safety is established by testing, not by origin.