Separate evidence from claims, expose the missing bridge and test the kinds of reasoning behind it.
GMAT45 min study guide9 indexed sections
BY THE END, YOU CAN
Explain and apply conclusion versus premise
Explain and apply intermediate conclusions
Explain and apply unstated assumptions
Explain and apply necessary versus sufficient conditions
Explain and apply correlation versus causation
Explain and apply alternative causes
Explain and apply sampling and representativeness
Explain and apply quantities versus percentages
BEFORE YOU START
Read an argument or passage without assuming that every speaker agrees.
Distinguish a claim from the evidence offered for it; interpret simple counts and percentages.
Original educational lesson. Work through the examples before revealing the practice answers. This original lesson supports current GMAT study through an editorial skill map. It does not reproduce official questions, predict exam content or guarantee a score.
LEARN THROUGH ORIGINAL PRACTICE
Original GMAT-style worked examples and practice
All passages, examples and exercises here are original. No official GMAC questions, choices or explanations are reproduced. This independent preparation resource is not affiliated with or endorsed by GMAC. GMAT is a trademark of the Graduate Management Admission Council.
01 / UNDERSTAND & APPLY
Premises and the conclusion
A premise is offered as support; a conclusion is what that support is intended to establish. Neither role depends on whether the statement is actually true. Ask “What is the writer trying to get me to accept?” and “What reason is offered?” Indicator words such as therefore and because help but are not mandatory.
An argument can contain background, an opposing view, a concession and a recommendation. Do not label every factual-looking sentence a premise of the author’s conclusion. A reported fact may support an opponent or merely set the scene.
Full-size scientific diagram. Swipe or scroll horizontally; keyboard users can focus the diagram and use arrow keys.
The conclusion predicts a new setting. The bridge is an assumption to investigate, not a fact supplied by the trial.
ORIGINAL WORKED EXAMPLE
Find the claim
A production trial found that a new filter reduced rejected batches on one line. The manager therefore recommends installing it on every line, predicting fewer rejected batches overall. Identify the evidence and conclusion.
Evidence: the observed reduction on the tested line.
Main conclusion: the recommendation and associated prediction for every line.
The trial does not itself establish transfer to different conditions; that is a bridge requiring support.
Answer The trial result is a premise; the broad rollout prediction supports the recommendation.
02 / UNDERSTAND & APPLY
Intermediate conclusions have two jobs
An intermediate conclusion is supported by an earlier premise and then used to support a later claim. Its dual role matters more than its position. Draw arrows: observation → interpretation → recommendation. The same sentence can be a conclusion relative to one claim and a premise relative to another.
Do not assume the final sentence is always the main conclusion. A speaker may state a recommendation first and then explain it. Use the support relationships, not sentence order.
ORIGINAL WORKED EXAMPLE
Map a chain
The town’s old pump consumes more electricity per liter than the new model in a controlled test. Therefore replacing it would reduce electricity use for the same volume. Since electricity savings would exceed the replacement cost over five years, the council should replace it. Identify the intermediate conclusion.
The test supports a prediction about reduced electricity use.
That prediction combines with the five-year savings premise to support replacement.
The recommendation is the final claim, not the test result.
Answer Replacing the pump would reduce electricity use for the same volume.
03 / UNDERSTAND & APPLY
The unstated bridge
An assumption is an unstated proposition the reasoning relies on. It is not simply any fact that would be interesting to know. In the filter example, the conclusion needs a reason to expect relevant benefits under rollout conditions. It does not need every production line to be identical in every respect.
Separate necessary assumptions from sufficient support. A necessary assumption must hold for the reasoning to work but may leave other gaps. A sufficient premise, with the stated premises, guarantees the conclusion in a deductive argument. Ordinary empirical arguments often provide degrees of support rather than guarantees.
ORIGINAL WORKED EXAMPLE
Avoid an overly strong assumption
Must the filter argument assume that all lines are physically identical?
Relevant differences must not defeat the predicted overall reduction.
Lines could differ in color, manufacturer or output yet all benefit.
An assumption of complete identity is stronger than required; the relevant issue is transfer of the effect.
Answer No. Relevant performance comparability is the issue, not total identity.
04 / UNDERSTAND & APPLY
Necessary and sufficient conditions
“If a shipment is priority, it is tracked” means priority → tracked. Priority status is sufficient for tracking under the rule; tracking is necessary for priority status. The valid contrapositive is not tracked → not priority. Neither tracked → priority nor not priority → not tracked follows.
“Only tracked shipments are priority” expresses the same rule. “A shipment is tracked only if it is priority” reverses it. Translate carefully before reasoning; “only if” introduces a necessary condition. A biconditional requires both directions, not one.
ORIGINAL WORKED EXAMPLE
Test a conditional inference
Every certified technician completed the safety course. Mira completed the course. Must Mira be certified?
Certification → course completion.
Course completion is compatible with certification but does not guarantee it; uncertified trainees could also complete the course.
This is affirming the consequent if treated as a proof.
Answer No; completing the course is necessary under the rule but not sufficient for certification.
05 / UNDERSTAND & APPLY
Correlation, causation and alternatives
A correlation is an association between variables. A causal conclusion claims that changing one produces a change in the other. Alternative explanations include reverse causation, a common cause, selection effects and chance. Naming an alternative is not proving it, but credible evidence for one can weaken an exclusive causal story.
A comparison is more informative when the groups are alike on relevant preexisting factors and the outcome is measured consistently. Random assignment can reduce selection bias, though implementation, attrition and sample size can still matter. Do not treat the word “study” as automatic proof.
ORIGINAL WORKED EXAMPLE
Find a common cause
Cafés with more outdoor tables have higher summer revenue. A consultant concludes that adding tables causes higher revenue. What alternative cause should be considered?
Busy tourist areas may produce both demand for outdoor seating and higher revenue.
That factor could generate the association even if merely adding tables elsewhere does not raise revenue.
The alternative needs investigation; its possibility does not prove that tables have no effect.
Answer Tourist-area location could explain both table count and revenue.
06 / UNDERSTAND & APPLY
Samples and representativeness
A survey supports claims about the surveyed group directly. Generalization requires evidence that selection and nonresponse do not distort the target trait. A large sample can still be biased if everyone is recruited from a special subgroup.
Specify the target population before judging representativeness. A survey of night-shift workers may be useful for night-shift preferences but weak evidence about all employees. The same sample can be suitable for one conclusion and unsuitable for another.
ORIGINAL WORKED EXAMPLE
Locate selection bias
A company surveys only employees who use its gym and finds most want longer gym hours. It concludes most employees want longer hours.
The surveyed population excludes nonusers, whose preferences may differ.
The conclusion expands the denominator from gym users to all employees.
More responses from the same restricted group do not automatically correct that selection problem.
Answer The sample may not represent all employees on the issue of gym hours.
07 / UNDERSTAND & APPLY
Quantities and percentages
A percentage is a part relative to a whole. A higher percentage can accompany a lower count, and a lower percentage can accompany a higher count. Before accepting a trend claim, write the numerator and denominator for each period.
For example, 20% of 100 returns is 20 defective items; 15% of 200 returns is 30 defective items. The defect share of returns fell while the count rose. Neither statistic alone tells the defect rate among all products sold. Different denominators answer different questions.
08 / UNDERSTAND & APPLY
Practice: dissect before judging
For each item identify the requested role or logical consequence.
ORIGINAL PRACTICE · 1
1. “The road is closed, so the delivery truck cannot use its usual route. Therefore the dispatch plan needs revision.” What is the intermediate conclusion?
Reveal answer & reasoning
The truck cannot use its usual route.
It follows from road closure and supports revising the plan. Road closure is the initial premise; revision is the final recommendation.
ORIGINAL PRACTICE · 2
2. Only audited accounts may receive a grant. Account Z received a grant under that rule. What follows?
Reveal answer & reasoning
Z was audited.
Grant receipt → audited. The reverse, audited → grant receipt, does not follow; an audited account might fail another requirement.
ORIGINAL PRACTICE · 3
3. All insulated containers in a shipment passed the test. Container Q failed. Could Q have been insulated within that shipment?
Reveal answer & reasoning
No.
The valid contrapositive is failed test → not insulated, for containers in the stated shipment. It says nothing about containers outside that scope.
ORIGINAL PRACTICE · 4
4. A survey of 5,000 newsletter subscribers finds strong approval of the newsletter. Does sample size alone justify a claim about all city residents?
Reveal answer & reasoning
No.
Subscribers are a selected group likely to differ in engagement. A large biased sample can remain unrepresentative.
ORIGINAL PRACTICE · 5
5. A defect share rises from 10% of 500 units to 15% of 200 units. Does the number of defective units rise?
Reveal answer & reasoning
No; it falls from 50 to 30.
0.10×500=50 and 0.15×200=30. The share rises while the denominator shrinks enough to reduce the count.
ORIGINAL PRACTICE · 6
6. Neighborhoods with more bike racks have more cyclists. Give one alternative to “racks caused cycling.”
Reveal answer & reasoning
Higher existing cycling demand may have led the city to install more racks.
This is reverse causation. A common cause, such as dense mixed-use development, could also be relevant, but the requested answer is one alternative.
09 / UNDERSTAND & APPLY
Practice: expose the bridge
Treat each argument’s premises as given; identify what additional reasoning is needed.
ORIGINAL PRACTICE · 1
7. “The pilot reduced errors among experienced staff; therefore it will reduce errors among newly hired staff.” What is the missing bridge?
Reveal answer & reasoning
The pilot’s error-reducing effect must transfer sufficiently to newly hired staff.
The target group changes. Total identity between groups is unnecessary, but differences in training or task familiarity must not defeat the prediction.
ORIGINAL PRACTICE · 2
8. “More customers chose our premium plan this year, so the premium plan’s share of customers rose.” What information is missing?
Reveal answer & reasoning
The total number of customers in each year.
Premium customers could rise from 20 of 100 to 30 of 300: count rises while share falls from 20% to 10%. The claimed share change needs denominators.
KEEP THE BIG IDEAS
Quick revision
Classify statements by their support roles, not their grammar or position.
An observed association needs additional support for a causal conclusion.
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