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Test causal rivals, sampling mismatches and plan obstacles without demanding that the conclusion become impossible.
Paper packet. Every task here also exists on screen, where it is checked automatically; answers written on paper are not assessed by Nydus. When you are back at a device, enter your answers there.
Find the addition that most undermines the route from the stated evidence to the conclusion.
Strengthening improved the support connection. Weakening asks what damages it. The original premises remain the starting point; you are usually adding a fact, not pretending the given observation never happened. Identify the exact causal, predictive or generalizing move before testing choices.
| Term | What it means |
|---|---|
| Confound | A relevant difference that can explain an apparent treatment effect. |
| Selection effect | A difference arising because people entering the compared groups were different beforehand. |
| Net effect | The combined result after relevant gains and losses are considered. |
| Counterexample | A case incompatible with a universal claim while meeting its stated conditions. |
An argument may reach a true conclusion for a poor reason. A weakening answer makes the offered reason less convincing; it need not prove the conclusion false. If people using a study app earn higher grades, evidence that they already had higher grades before using it weakens the claim that the app caused the difference. The users can still have high grades, and the app could still have some benefit. The observed association alone now carries less causal weight.
Read which claim the author actually makes. Evidence against a guarantee may not damage a modest claim about a small improvement. An exception to all is decisive for a universal conclusion, but an exception to most may be compatible with it. A cost increase matters to a net-benefit argument only when it affects the relevant comparison. Specificity prevents choosing an answer that attacks a stronger argument than the author offered.
Accept the new fact, identify the connection it changes, and compare its effect with the alternatives. A fact that makes the situation unpleasant is not necessarily a weakener. A fact that supplies another route to the same outcome can weaken a causal attribution even while making the outcome more likely.
Another way: picture
Draw the observation on the left and the proposed explanation on the right. A rival arrow from another cause to the observation shows why the observation may no longer discriminate between explanations.
Another way: steps
State the inference; locate a vulnerable link; add each fact separately; explain the damage; retain the fact that most directly undermines the actual conclusion.
A sound weakening analysis preserves the observation while reducing the confidence it warrants in the conclusion. Suppose a tutoring service advertises higher scores among its users. Learning that the service admitted only students with high previous scores does not deny the new scores. It changes what those scores show about the service's contribution. The comparison might still be compatible with a benefit, but the selected groups no longer provide the clean contrast the advertisement implies.
Now compare a different answer: some users disliked the tutor's voice. That fact may sound negative without explaining the measured score difference. A dislike could coexist with effective instruction. The question is not which fact makes the service look least appealing; it is which fact most damages the reasoning offered. Keeping that distinction explicit prevents emotional vocabulary from replacing analysis.
A similar trap arises with costs. If an author predicts increased attendance, evidence of higher operating cost may be irrelevant to that narrow prediction. If the conclusion instead predicts increased profit, the cost can be central. Restate the target before evaluating the same piece of information. An answer can be a strong objection to adopting a plan while being a poor objection to one specific prediction made about it.
When two candidates seem plausible, identify the extra assumption needed for each to matter. An answer saying that a proposed bus route passes near workplaces has no fixed weakening effect without knowing who travels and when. An answer saying its intended passengers cannot use the route during their work hours identifies a direct obstacle. Prefer the supported connection over an imagined story. This does not mean the best answer always contains more detail; it means its relevant detail actually reaches the vulnerable step in the argument.
An alternative cause can explain why two things occur together. Selection can explain a group difference when people choose whether to receive a treatment. Reverse causation can explain an association when the supposed outcome instead influences the proposed cause. A common cause can produce both measured features. These are different patterns, so name the one the answer actually supports.
A changed measurement method can also explain an apparent improvement. If inspectors stopped counting minor defects, a lower reported defect count does not necessarily show better production. That challenges what the observed count establishes without denying that the reported count fell. Do not invent an alternative unsupported by the answer choice; the task supplies the additional evidence you may use.
For a survey argument, compare the sample with the target group. A large response count does not remove a relevant selection difference. To weaken a population inference, evidence should connect the selection feature to the opinion or behavior being measured. Merely saying the sample differs in an unrelated characteristic may not matter.
For a plan, trace the whole mechanism. Lower prices may raise demand but lower revenue if sales cannot increase enough. A free shuttle may remove transport cost but leave opening hours as the actual obstacle. Show precisely where the proposed action fails to produce its intended outcome. A disadvantage unrelated to the stated objective may be a reason to dislike the plan, but it does not automatically undermine the prediction.
Weakening is relative to the original support. A rival explanation need not be proved beyond all doubt to make a causal conclusion less secure. Yet a remote possibility with no connection to the evidence is usually weaker than a documented confound. Compare answers on relevance and inferential impact rather than on emotional force.
Do not choose a fact that strengthens the conclusion because it mentions a familiar weakness. A well-matched randomized comparison may remove the very selection problem you were looking for. Read the direction of the finding. Also distinguish a challenge to evidence from a personal attack: an author's unpopular views do not by themselves undermine a carefully measured result.
Suppose a service advertises a before-and-after improvement. Identify the outcome, the comparison and the causal conclusion before reacting to the size of the change. Look for what else changed and whether the same measurement rules were used. A dramatic number can coexist with weak attribution.
The exercise is not an invitation to reject every claim. A good weakener identifies a specific evidential limitation, while a good response to that weakener would address the limitation. Keep an error record that distinguishes selection, common cause, measurement change, population mismatch and implementation failure. The automatic records check your supplied-option judgments, not your ability to conduct an investigation. On a later attempt, apply the same method to the new scenario instead of remembering which option position was correct. A missed question is most useful when you can name the link you failed to inspect.
Do not deny a stipulated premise, demand proof that the conclusion is impossible, or confuse an unrelated disadvantage with damage to the stated prediction. Check whether the new evidence moves support up or down.
Read the passage and question.
Students attending an optional revision session scored higher than students who skipped it. A tutor says the session caused the entire difference.
Which finding most weakens the claim?
The observed difference is accepted; the question is what produced it.
Compare the five proposed answers.
1: Attendees scored higher by the same margin on a comparable test before the session. 2: The session included practice questions. 3: The tutor prepared carefully. 4: Randomly assigned attendees improved more than controls. 5: The room had many chairs.
Apply the question's test to each option; do not choose solely by shared vocabulary.
Explain the best answer.
Attendees scored higher by the same margin on a comparable test before the session.
The preexisting gap supplies a selection explanation for the later difference.
Account for every rejected answer.
2: That is compatible with effectiveness and does not expose selection. 3: Preparation does not isolate the cause of the score gap. 4: This finding would support a causal effect. 5: The room's furnishing does not bear on the inferential gap.
Each rejection identifies a specific mismatch with the passage or task.
Read the passage and question.
A ferry predicts that cutting fares will increase total daily revenue because more people will want to travel.
Which fact most weakens this prediction?
Keep the conclusion as revenue rather than popularity or passenger interest.
Compare the five proposed answers.
1: All daily sailings are already full and no extra sailings can be added. 2: Travelers prefer lower fares. 3: The ferry has a distinctive logo. 4: The water crossing is scenic. 5: The operator has sold tickets for years.
Apply the question's test to each option; do not choose solely by shared vocabulary.
Explain the best answer.
All daily sailings are already full and no extra sailings can be added.
The proposed extra demand cannot produce additional passengers, leaving the fare reduction uncompensated.
Account for every rejected answer.
2: Preference supports demand but does not overcome capacity. 3: Brand design does not establish the revenue effect. 4: Scenery does not determine whether extra demand can become sales. 5: Experience alone does not repair the capacity problem.
Each rejection identifies a specific mismatch with the passage or task.
Read the passage and question.
A city surveys members of a downtown business association and concludes that most residents favor longer shop opening hours.
Which finding most weakens the generalization?
A relevant sampling difference matters more than size alone.
Compare the five proposed answers.
1: Association members favor longer hours far more often than the residential population outside that association. 2: The survey used a large font. 3: The association has many members. 4: A representative residents' survey found the same majority. 5: The city has several shopping streets.
Apply the question's test to each option; do not choose solely by shared vocabulary.
Explain the best answer.
Association members favor longer hours far more often than the residential population outside that association.
The sample's selection is tied to the very preference generalized to residents.
Account for every rejected answer.
2: Readability does not establish representativeness. 3: A large biased frame can remain biased. 4: Independent representative agreement would strengthen the conclusion. 5: Street count does not establish the distribution of resident views.
Each rejection identifies a specific mismatch with the passage or task.
Check the difficult boundary.
The weakener undermines extrapolation from association members; it does not prove that every other resident opposes longer hours.
This last check preserves the exact strength and scope of the answer rather than turning it into a broader claim.
Trace the proposed mechanism.
A school offers free transport to an evening event to attract families who cannot attend.
The plan treats transport cost as the attendance barrier.
Identify the weakening fact.
Most nonattending families work during the event, and its hours will not change.
The action leaves the major identified barrier in place.
State the limited result.
Residents who joined a neighborhood walking group reported better sleep than residents who did not. The organizer concludes that joining the group caused better sleep. Which finding most weakens the causal conclusion?
A town expects a cheaper parking rate to increase parking revenue because more drivers will use the lot. Which fact most weakens the prediction?
A store claims a new display increased sales because sales rose in the month after installation. Which fact most weakens that causal claim?
A hospital reports fewer scheduling errors after adopting new software. The director concludes that the software reduced the error rate per appointment. Which evidence most weakens the conclusion?
A council predicts that free parking will bring more shoppers downtown, increasing total sales. It assumes the new spaces will mainly serve shoppers. Which fact most weakens the prediction?
A museum surveyed visitors who bought exhibition catalogues. Most wanted more technical labels. The museum concludes most visitors want more technical labels. Which finding most weakens the inference?
A mayor argues that extending café hours will reduce empty storefronts because a neighboring district saw vacancies fall after extending hours. Which fact most weakens the comparison?
A café observes that revenue rose after it introduced reusable cups. It credits the cups for the entire increase. Which finding most weakens that explanation?
A bakery moves its proofing trays to a temperature-controlled cabinet and subsequently fewer loaves collapse. During the same period it also begins using a stronger flour. A coordinator concludes that the intervention caused the improvement, arguing that stable proofing temperature prevents excessive expansion. Which finding most weakens the coordinator's explanation?
A coastal rescue station adds reflective markers to its landing route and subsequently crews reach the dock faster at night. During the same period it also introduces a navigation refresher course. A coordinator concludes that the intervention caused the improvement, arguing that markers make the approach easier to identify in darkness. Which finding most weakens the coordinator's explanation?
A magazine polls its online subscribers and concludes that most adults in the region support a new cycling route. Which fact most weakens the generalization?
Answer three reserved questions without hints. These cases are separate from lesson practice.
A town credits its new traffic signs for fewer collisions, citing the lower total after installation. Which finding most weakens the claim?
A publisher concludes that readers prefer short books because short books sold more copies than long books last month. Which fact most weakens the inference?
A museum plans to increase attendance by offering a free shuttle from a distant car park, assuming transport cost keeps prospective visitors away. Which finding most weakens the plan's rationale?
Tomorrow, recall one way to weaken a causal claim, one way to weaken a population claim and one obstacle to a plan. Next, describe a flaw already present rather than adding a new fact.
14. Find the remaining obstacle, step 3
Free transport may help some families, but the predicted broad increase has less support.
A plan need not be completely useless for its argument to weaken.