Philosophy Quiz: Inductive Reasoning
20 questions · exam conditions
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Inductive ReasoningQuestion 1 of 20

Upon returning from a week-long vacation, a homeowner discovers their house is unusually cold and their houseplants are dead. They also notice that the digital clocks on the microwave and oven are blinking '12:00'. They conclude that there must have been a power outage while they were away.

The homeowner's conclusion is best described as which of the following?

A weak induction, because it fails to consider alternative explanations, such as a faulty thermostat or neglect of the plants.
A strong inference to the best explanation, because a single event (a power outage) cohesively explains all the available evidence.
A deductively valid inference, as the evidence logically guarantees that a power outage must have occurred.
A strong inductive generalization, because it reasonably extends from specific observations to a general conclusion about the past.
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Philosophy Quiz

Philosophy Quiz: Inductive Reasoning

Practice Inductive Reasoning in Philosophy with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Inductive Reasoning, giving you a quick way to practice the rules, question types, and explanations that matter most for Philosophy.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Upon returning from a week-long vacation, a homeowner discovers their house is unusually cold and their houseplants are dead. They also notice that the digital clocks on the microwave and oven are blinking '12:00'. They conclude that there must have been a power outage while they were away.

The homeowner's conclusion is best described as which of the following?

  1. A weak induction, because it fails to consider alternative explanations, such as a faulty thermostat or neglect of the plants.
  2. A strong inference to the best explanation, because a single event (a power outage) cohesively explains all the available evidence. (correct answer)
  3. A deductively valid inference, as the evidence logically guarantees that a power outage must have occurred.
  4. A strong inductive generalization, because it reasonably extends from specific observations to a general conclusion about the past.
Explanation: This is an example of a strong inference to the best explanation (abduction). The conclusion—a power outage—is strong because it is a single, simple explanation that accounts for all the disparate pieces of evidence: the cold house (heater reset), dead plants (lack of light/heat), and blinking clocks (loss of power). Alternative explanations (distractor A) are less comprehensive; a faulty thermostat wouldn't explain the blinking clocks or dead plants, for instance.

Question 2

A political analyst argues: 'In every presidential election since 1960, the candidate who was taller has won. The current challenger is taller than the incumbent. Therefore, the challenger will win the upcoming election.'

The analyst's argument should be evaluated as...

  1. weak, because the observed correlation between height and winning is likely spurious and lacks a plausible causal connection. (correct answer)
  2. strong, because it is based on a consistent, unbroken pattern of evidence spanning over 60 years.
  3. strong, because it provides a testable prediction, which is the hallmark of a good scientific induction.
  4. weak, because the sample size (the number of elections) is too small to establish a meaningful pattern.
Explanation: When evaluating arguments based on correlations or patterns, you need to distinguish between mere statistical associations and genuine causal relationships. The strength of an argument depends not just on consistent data, but on whether there's a plausible explanatory mechanism. The analyst's argument is fundamentally weak because it confuses correlation with causation. While the height pattern may be statistically accurate, there's no credible causal mechanism explaining why being taller would make someone more likely to win a presidential election. Height doesn't directly influence policy positions, debate performance, or voter decision-making in meaningful ways. This makes the correlation spurious—appearing meaningful but actually coincidental. Answer A correctly identifies this fatal flaw. Answer B is wrong because consistency alone doesn't make an argument strong. Even a perfect correlation can be meaningless without causal plausibility. A consistent pattern of coincidences is still just coincidence. Answer C misapplies scientific methodology. While the prediction is technically testable, testability alone doesn't validate an argument. Scientific induction requires both empirical testing AND theoretical grounding—a plausible mechanism explaining why the pattern should continue. Answer D focuses on sample size, but this misses the main issue. Even with more elections, a spurious correlation would remain spurious. The fundamental problem isn't insufficient data but the absence of any logical connection between height and electoral success. Remember: when evaluating correlational arguments, always ask "Is there a plausible reason this pattern should continue?" Strong arguments need both empirical support and logical coherence.

Question 3

Statement: 'Every time I've eaten at 'The Greasy Spoon' diner, I've gotten indigestion. I'm never eating there again, because their food will just give me indigestion.'

The reasoning in this statement would be most weakened if which of the following were true?

  1. The speaker has only eaten at the diner three times over a period of five years.
  2. The speaker's dining companion, who ate the same meals, never got indigestion.
  3. The diner has passed all of its health inspections with excellent scores.
  4. On each occasion, the speaker had a very stressful meeting immediately before eating at the diner. (correct answer)
Explanation: The argument makes a causal claim: the diner's food causes the speaker's indigestion. This is based on a correlation. A strong inductive argument requires ruling out alternative causes. Option D provides a plausible alternative cause for the indigestion: stress. If the indigestion is caused by stress rather than the food, the inductive link in the argument is severely weakened. Option A (sample size) and B (different physiology) weaken it slightly, but D provides a direct alternative causal explanation for the observed effect in the speaker.

Question 4

An art expert examines a newly discovered painting attributed to a famous 17th-century master. The expert notes the brushwork is consistent with the master's style, the canvas and pigments are age-appropriate, and an 'X-ray' reveals an under-drawing similar to the master's known sketches. The expert concludes the painting is authentic.

The expert's reasoning is strong because it...

  1. provides a deductively valid proof of the painting's authenticity based on the evidence.
  2. relies on an argument from authority, as the expert's opinion is the primary evidence.
  3. accumulates multiple, independent lines of evidence that all converge on the same conclusion. (correct answer)
  4. generalizes from a single case to make a broad claim about the artist's entire body of work.
Explanation: This is a strong inductive argument based on inference to the best explanation. Its strength comes from the convergence of multiple, independent pieces of evidence (brushwork, materials, under-drawing). Each piece of evidence on its own provides some support, but together they make the conclusion that the painting is authentic much more probable than any other explanation (e.g., an incredibly skilled forgery). This accumulation of converging evidence is a key feature of strong inductive arguments in fields like history, science, and law.

Question 5

A mechanic is diagnosing a sputtering engine. They know that this is usually caused by either a clogged fuel filter or old spark plugs. They replace the fuel filter, but the engine still sputters. They then conclude that the problem must be the old spark plugs.

The mechanic's reasoning is best described as...

  1. A weak induction, because replacing the fuel filter could have introduced a new problem.
  2. A deductively valid argument, specifically a disjunctive syllogism.
  3. A strong inductive argument that proceeds by eliminating one of the most probable explanations. (correct answer)
  4. A hasty generalization, as they have only considered two possible causes for the problem.
Explanation: The mechanic's reasoning is a strong form of inductive inference often used in diagnostics. They start with a limited set of likely hypotheses ('P or Q'). They then gather evidence that eliminates one hypothesis ('Not P'). They conclude the other hypothesis is likely true ('Therefore, probably Q'). This is not deductively valid (as in B, a disjunctive syllogism) because the initial premise ('the cause is P or Q') is itself an inductive assumption; there could be another unknown cause. However, assuming the initial assessment of probable causes is good, the reasoning is inductively strong. D is incorrect because this isn't a generalization, but an inference to a specific cause.

Question 6

Two drug trials are conducted for a new headache medicine. Trial A uses 20 subjects. Trial B uses 2,000 subjects. In both trials, the subjects are randomly selected from the general population, and both are double-blind, placebo-controlled studies. Both trials find that the medicine is effective.

Based on this information, how does the evidence from Trial B affect the conclusion that the medicine is effective?

  1. It weakens the conclusion because a larger sample is more likely to reveal negative side effects.
  2. It provides stronger inductive support for the conclusion due to the larger and more representative sample size. (correct answer)
  3. It has no effect on the strength of the conclusion, as both trials were properly controlled and reached the same result.
  4. It provides weaker inductive support because managing a larger trial is more prone to experimental errors.
Explanation: In inductive generalizations, such as those in scientific testing, the size and representativeness of the sample are crucial to the strength of the evidence. A larger, well-selected sample (like in Trial B) provides stronger evidence and allows for a more confident generalization from the sample to the entire population than a smaller sample (like in Trial A). Therefore, the evidence from Trial B provides much stronger inductive support for the conclusion.

Question 7

A study analyzed the diets of 10,000 people and found a strong correlation between high coffee consumption and a lower incidence of a certain neurological disease. The study concludes that drinking coffee helps prevent the disease.

Which of the following, if true, would most seriously weaken the study's inductive conclusion?

  1. The study did not differentiate between caffeinated and decaffeinated coffee.
  2. The study was funded by a large international coffee-growers association.
  3. The study found that people who drink a lot of coffee also tend to exercise more regularly than those who do not. (correct answer)
  4. The study's participants were all from the same geographical region.
Explanation: The conclusion is a causal one based on a correlation. Its strength depends on ruling out alternative explanations. Option C provides a plausible confounding variable: regular exercise. It is known that exercise has neurological benefits. If coffee drinkers also exercise more, then the exercise—not the coffee—could be the cause of the lower disease incidence. This alternative explanation significantly weakens the original causal inference. B suggests a potential for bias but doesn't weaken the logical connection itself. A and D point to limitations but are less damaging than a plausible confounding cause.

Question 8

Consider the argument: 'Every raven that has ever been observed by a scientist is black. Therefore, the next raven we observe will be black.'

Which of the following statements most accurately evaluates this argument?

  1. It is a deductively valid argument because the conclusion is guaranteed by the premise.
  2. It is a weak inductive argument because the future is unpredictable and the next raven could be an albino.
  3. It is a strong inductive argument because the premise provides a very high degree of probability for the conclusion. (correct answer)
  4. It is an uncogent argument because the premise, while true, does not logically support the conclusion.
Explanation: This is a classic example of a strong inductive argument. The premise, based on a vast and uniform set of observations, makes the conclusion extremely probable, although not certain. This is the hallmark of a strong induction. Distractor B incorrectly identifies it as weak; while the conclusion isn't certain, inductive strength is about probability, and the probability here is very high. Distractor A incorrectly classifies it as deductive. Distractor D misuses the term 'uncogent'; an uncogent argument can be strong but have false premises, but here the premise is true and it does support the conclusion.

Question 9

A social scientist conducts a survey at a large, politically active environmentalist rally. They ask 1,000 attendees if they believe urgent, large-scale government action is needed to combat climate change. 98% of the respondents answer 'yes'. The scientist concludes that 'the vast majority of citizens support urgent, large-scale government action on climate change'.

Which of the following provides the most accurate evaluation of the scientist's inductive argument?

  1. The argument is strong because the sample size of 1,000 participants is statistically significant and provides a low margin of error.
  2. The argument is weak because the sample is not representative of the general population, introducing significant selection bias. (correct answer)
  3. The argument is strong because the conclusion is consistent with findings from major international scientific bodies on climate change.
  4. The argument is weak because the question is leading and encourages a specific answer from respondents.
Explanation: The argument is a weak inductive generalization. While the sample size is large, the evidence is drawn from a highly unrepresentative sample. People at an environmentalist rally are far more likely to hold strong views on climate action than the general population. This selection bias means the conclusion about 'the vast majority of citizens' is not well-supported by the evidence provided. A strong induction requires a sample that is representative of the target population.

Question 10

Argument: 'My friend's new high-performance sports car, a V8-powered 'Inferno GT', has been very unreliable and required numerous expensive repairs. Therefore, my other friend, who just bought a practical, four-cylinder 'EcoWagon' sedan from the same manufacturer, will likely experience similar reliability issues.'

How should the strength of this inductive argument be characterized?

  1. Strong, because both vehicles are made by the same manufacturer, suggesting similar engineering and quality control standards across models.
  2. Weak, because it is an argument from analogy where the relevant dissimilarities between the vehicles likely outweigh the similarities. (correct answer)
  3. Strong, because it correctly identifies a potential risk based on a documented case, which is a key function of inductive reasoning.
  4. Weak, because it is a hasty generalization based on a sample size of only one vehicle, which is insufficient for any conclusion.
Explanation: This is a weak argument from analogy. The strength of such an argument depends on the relevant similarities between the two things being compared. In this case, while the manufacturer is the same, the cars are very different types: a high-performance sports car and a practical sedan. These differences in design, engineering, and intended use are highly relevant to reliability, making the comparison weak. Distractor D is plausible but less precise; the core flaw is the weak analogy between dissimilar objects, not just the sample size.

Question 11

An investor observes that for the past five years, a particular stock's value has increased by at least 15% during the month of January. The investor concludes, 'Therefore, this stock's value will increase by at least 15% this coming January.'

Suppose that, unexpectedly, a massive international crisis occurs in December, causing the entire stock market to crash. How does this new information affect the investor's original argument?

  1. It has no effect on the argument's inductive strength, because the argument is based on historical data which has not changed.
  2. It renders the argument deductively invalid, because the conclusion is now certain to be false.
  3. It significantly weakens the argument by introducing new, relevant evidence that the original argument did not account for. (correct answer)
  4. It proves the original argument was a logical fallacy, specifically post hoc ergo propter hoc.
Explanation: This question tests the role of the total evidence requirement in induction. A strong inductive argument must consider all available relevant evidence. The original argument, based solely on past performance, might have been moderately strong. However, the new information about a market crash is highly relevant and undermines the expectation of continued growth. By failing to account for this new evidence, the argument becomes very weak.

Question 12

A city observes that ice cream sales are highest during the same months that drowning incidents are most frequent. An official proposes, 'To reduce drowning deaths, we must limit the sale of ice cream.'

The official's reasoning from the evidence to the conclusion is weak primarily because it...

  1. relies on a sample size that is too small, as it only considers data from a single city.
  2. commits a post hoc ergo propter hoc fallacy, assuming that one event caused another just because it occurred first.
  3. fails to consider a common cause, warm weather, that is likely responsible for the increase in both variables. (correct answer)
  4. makes a strong inductive connection, as the correlation between the two variables is consistently observed and statistically significant.
Explanation: This is a classic example of confusing correlation with causation due to a confounding variable (or common cause). The argument is weak because it fails to recognize that a third factor, warm weather, leads to both increased ice cream sales and increased swimming (and thus more drowning incidents). The correlation is real, but the causal inference is flawed. Distractor C accurately identifies this flaw. Distractor B is incorrect because the events happen concurrently, not one after the other, making 'common cause' a better description of the flaw than post hoc.

Question 13

To argue that a proposed law requiring all motorcyclists to wear helmets is a good idea, a politician states: 'Requiring professional football players to wear helmets dramatically reduced head injuries in that sport. Similarly, requiring motorcyclists to wear helmets will dramatically reduce head injuries in riding.'

The politician's argument is best classified as which of the following, and what is its primary determinant of strength?

  1. An inductive generalization, whose strength depends on the number of football players observed.
  2. An inference to the best explanation, whose strength depends on ruling out other reasons for football's safety record.
  3. A deductive argument, whose strength depends on the truth of the premise about football.
  4. An argument from analogy, whose strength depends on the relevant similarities between playing football and riding a motorcycle. (correct answer)
Explanation: When you encounter arguments that draw comparisons between different situations, you're likely dealing with analogical reasoning. The key is identifying what type of logical structure the argument follows and what factors determine its persuasive power. The politician's argument follows a clear analogical pattern: helmets reduced injuries in football, therefore helmets will reduce injuries in motorcycling. This creates a comparison between two activities to justify a conclusion about one based on evidence from the other. The strength of this argument hinges entirely on how similar football and motorcycling actually are in relevant ways—both involve head injury risks, both benefit from protective gear, both involve high-impact activities. The more relevant similarities exist, the stronger the analogy becomes. Let's examine why the other options miss the mark. Choice A incorrectly identifies this as inductive generalization, which would involve drawing conclusions about a whole group from observations of some members—but the politician isn't generalizing about helmet-wearers broadly. Choice B mischaracterizes this as inference to the best explanation, which seeks the most likely cause for observed phenomena—the politician isn't trying to explain why something happened. Choice C calls this deductive reasoning, but deductive arguments guarantee their conclusions if premises are true, while analogies only suggest probable outcomes. Remember this pattern: when an argument uses "similarly" or draws parallels between two different contexts to make a point, you're dealing with analogical reasoning. Always ask yourself how relevant the similarities are between the compared situations.

Question 14

Consider two inductive generalizations. Argument 1 concludes that 60% of a town's voters support Candidate X, based on a random poll of 1,000 residents. Argument 2 concludes that 60% of the town's voters support Candidate X, based on a poll of 1,000 attendees at a rally for Candidate X. Assuming both polls were conducted accurately, which statement is the best evaluation?

  1. Argument 1 is strong because its evidence is based on a representative sample, while Argument 2 is weak because its evidence is from a biased sample. (correct answer)
  2. Both arguments are equally strong because they use the same large sample size and arrived at the same conclusion.
  3. Argument 2 is stronger because it samples people who are more politically informed, making their responses more reliable.
  4. Both arguments are weak because a sample of 1,000 is insufficient to make a claim about an entire town's voter base.
Explanation: When evaluating inductive arguments, the strength depends heavily on whether your sample accurately represents the population you're drawing conclusions about. Inductive reasoning moves from specific observations to general conclusions, so the quality of those specific observations is crucial. Argument 1 uses a random sample of 1,000 residents, which gives every voter an equal chance of being included. This creates a representative sample that likely reflects the town's actual voting preferences. Random sampling is the gold standard because it minimizes bias and allows you to generalize confidently from your sample to the broader population. Argument 2, despite having the same sample size, polls only rally attendees. This creates selection bias—people at a candidate's rally are already supporters, so finding that 60% support that candidate tells you nothing surprising about the general population. The sample is systematically unrepresentative. Choice A correctly identifies that Argument 1 is strong due to its representative sample while Argument 2 is weak due to bias. Choice B falls into the trap of thinking sample size alone determines argument strength—but a large biased sample is still problematic. Choice C wrongly assumes political engagement equals reliability when the real issue is bias. Choice D incorrectly dismisses both arguments based on sample size; 1,000 is actually quite robust for most town populations when properly randomized. Remember: in inductive reasoning, representativeness trumps sample size. A smaller random sample beats a larger biased one every time. Always ask whether the sample could reasonably reflect the target population's characteristics.

Question 15

A detective concludes that a suspect is guilty based on three pieces of evidence: the suspect had a strong motive, owned the same type of weapon used in the crime, and was seen near the crime scene. Which of the following pieces of new evidence, if discovered, would make the detective's conclusion inductively stronger?

  1. The suspect's fingerprints, and no one else's, are found on the handle of the murder weapon. (correct answer)
  2. A witness comes forward who claims to have seen someone who looked vaguely like the suspect arguing with the victim a week before the crime.
  3. It is discovered that the suspect has no criminal record and is described by friends as a gentle person.
  4. Forensic analysis reveals that the type of weapon owned by the suspect is extremely common in the city.
Explanation: When you encounter questions about inductive reasoning, remember that inductive arguments become stronger when additional evidence increases the probability that the conclusion is true. Unlike deductive arguments that aim for certainty, inductive arguments build cumulative probability through multiple supporting pieces of evidence. The detective already has circumstantial evidence pointing toward guilt. To make this inductive argument stronger, you need evidence that directly connects the suspect to the crime itself, not just to general circumstances around it. Answer A provides exactly this type of strengthening evidence. Finding the suspect's fingerprints—and only the suspect's fingerprints—on the murder weapon creates a direct physical link between the suspect and the crime. This transforms the case from purely circumstantial (motive, weapon type, location) to including concrete physical evidence of the suspect's interaction with the actual murder weapon. Answer B is too weak and vague. A witness seeing someone who "looked vaguely like" the suspect a week before the crime adds minimal probative value and doesn't strengthen the connection to the actual murder. Answer C actively weakens the inductive argument by providing character evidence that contradicts the conclusion of guilt. A clean record and gentle reputation make guilt less probable, not more. Answer D also weakens the argument by showing that weapon ownership is common, making this piece of evidence less distinctive and therefore less probatively valuable. Remember: in inductive reasoning questions, look for evidence that most directly increases the probability of the conclusion being true, especially evidence that moves from circumstantial to direct physical proof.

Question 16

Argument: 'My friend's new high-performance sports car, a V8-powered 'Inferno GT', has been very unreliable and required numerous expensive repairs. Therefore, my other friend, who just bought a practical, four-cylinder 'EcoWagon' sedan from the same manufacturer, will likely experience similar reliability issues.'

How should the strength of this inductive argument be characterized?

  1. Strong, because both vehicles are made by the same manufacturer, suggesting similar engineering and quality control standards across models.
  2. Weak, because it is an argument from analogy where the relevant dissimilarities between the vehicles likely outweigh the similarities. (correct answer)
  3. Strong, because it correctly identifies a potential risk based on a documented case, which is a key function of inductive reasoning.
  4. Weak, because it is a hasty generalization based on a sample size of only one vehicle, which is insufficient for any conclusion.
Explanation: This is a weak argument from analogy. The strength of such an argument depends on the relevant similarities between the two things being compared. In this case, while the manufacturer is the same, the cars are very different types: a high-performance sports car and a practical sedan. These differences in design, engineering, and intended use are highly relevant to reliability, making the comparison weak. Distractor D is plausible but less precise; the core flaw is the weak analogy between dissimilar objects, not just the sample size.

Question 17

A city observes that ice cream sales are highest during the same months that drowning incidents are most frequent. An official proposes, 'To reduce drowning deaths, we must limit the sale of ice cream.'

The official's reasoning from the evidence to the conclusion is weak primarily because it...

  1. relies on a sample size that is too small, as it only considers data from a single city.
  2. commits a post hoc ergo propter hoc fallacy, assuming that one event caused another just because it occurred first.
  3. fails to consider a common cause, warm weather, that is likely responsible for the increase in both variables. (correct answer)
  4. makes a strong inductive connection, as the correlation between the two variables is consistently observed and statistically significant.
Explanation: This is a classic example of confusing correlation with causation due to a confounding variable (or common cause). The argument is weak because it fails to recognize that a third factor, warm weather, leads to both increased ice cream sales and increased swimming (and thus more drowning incidents). The correlation is real, but the causal inference is flawed. Distractor C accurately identifies this flaw. Distractor B is incorrect because the events happen concurrently, not one after the other, making 'common cause' a better description of the flaw than post hoc.

Question 18

A mechanic is diagnosing a sputtering engine. They know that this is usually caused by either a clogged fuel filter or old spark plugs. They replace the fuel filter, but the engine still sputters. They then conclude that the problem must be the old spark plugs.

The mechanic's reasoning is best described as...

  1. A weak induction, because replacing the fuel filter could have introduced a new problem.
  2. A deductively valid argument, specifically a disjunctive syllogism.
  3. A strong inductive argument that proceeds by eliminating one of the most probable explanations. (correct answer)
  4. A hasty generalization, as they have only considered two possible causes for the problem.
Explanation: The mechanic's reasoning is a strong form of inductive inference often used in diagnostics. They start with a limited set of likely hypotheses ('P or Q'). They then gather evidence that eliminates one hypothesis ('Not P'). They conclude the other hypothesis is likely true ('Therefore, probably Q'). This is not deductively valid (as in B, a disjunctive syllogism) because the initial premise ('the cause is P or Q') is itself an inductive assumption; there could be another unknown cause. However, assuming the initial assessment of probable causes is good, the reasoning is inductively strong. D is incorrect because this isn't a generalization, but an inference to a specific cause.

Question 19

Two drug trials are conducted for a new headache medicine. Trial A uses 20 subjects. Trial B uses 2,000 subjects. In both trials, the subjects are randomly selected from the general population, and both are double-blind, placebo-controlled studies. Both trials find that the medicine is effective.

Based on this information, how does the evidence from Trial B affect the conclusion that the medicine is effective?

  1. It weakens the conclusion because a larger sample is more likely to reveal negative side effects.
  2. It provides stronger inductive support for the conclusion due to the larger and more representative sample size. (correct answer)
  3. It has no effect on the strength of the conclusion, as both trials were properly controlled and reached the same result.
  4. It provides weaker inductive support because managing a larger trial is more prone to experimental errors.
Explanation: In inductive generalizations, such as those in scientific testing, the size and representativeness of the sample are crucial to the strength of the evidence. A larger, well-selected sample (like in Trial B) provides stronger evidence and allows for a more confident generalization from the sample to the entire population than a smaller sample (like in Trial A). Therefore, the evidence from Trial B provides much stronger inductive support for the conclusion.

Question 20

A detective concludes that a suspect is guilty based on three pieces of evidence: the suspect had a strong motive, owned the same type of weapon used in the crime, and was seen near the crime scene. Which of the following pieces of new evidence, if discovered, would make the detective's conclusion inductively stronger?

  1. The suspect's fingerprints, and no one else's, are found on the handle of the murder weapon. (correct answer)
  2. A witness comes forward who claims to have seen someone who looked vaguely like the suspect arguing with the victim a week before the crime.
  3. It is discovered that the suspect has no criminal record and is described by friends as a gentle person.
  4. Forensic analysis reveals that the type of weapon owned by the suspect is extremely common in the city.
Explanation: When you encounter questions about inductive reasoning, remember that inductive arguments become stronger when additional evidence increases the probability that the conclusion is true. Unlike deductive arguments that aim for certainty, inductive arguments build cumulative probability through multiple supporting pieces of evidence. The detective already has circumstantial evidence pointing toward guilt. To make this inductive argument stronger, you need evidence that directly connects the suspect to the crime itself, not just to general circumstances around it. Answer A provides exactly this type of strengthening evidence. Finding the suspect's fingerprints—and only the suspect's fingerprints—on the murder weapon creates a direct physical link between the suspect and the crime. This transforms the case from purely circumstantial (motive, weapon type, location) to including concrete physical evidence of the suspect's interaction with the actual murder weapon. Answer B is too weak and vague. A witness seeing someone who "looked vaguely like" the suspect a week before the crime adds minimal probative value and doesn't strengthen the connection to the actual murder. Answer C actively weakens the inductive argument by providing character evidence that contradicts the conclusion of guilt. A clean record and gentle reputation make guilt less probable, not more. Answer D also weakens the argument by showing that weapon ownership is common, making this piece of evidence less distinctive and therefore less probatively valuable. Remember: in inductive reasoning questions, look for evidence that most directly increases the probability of the conclusion being true, especially evidence that moves from circumstantial to direct physical proof.