The recurring flaw patterns
Correlation-to-causation: the argument observes two things happening together and concludes one caused the other, without ruling out a third factor, reverse causation, or coincidence.
Necessary-for-sufficient confusion: the argument treats a condition that's merely required (like 'top performers all attended this training') as though it guarantees the outcome for anyone who meets it.
Unrepresentative sample: the argument generalizes from a small, self-selected, or otherwise unusual group to a broader population that may differ in relevant ways.
Match the abstract description, not the topic
Answer choices describe the flaw in general terms ('presumes that a condition sufficient for a result is also necessary for it') rather than naming the subject matter. Translate the argument into your own plain description of the error first, then find the choice that matches that description, not the one that merely mentions the same nouns.
What LSAC says about identifying flaws
LSAC lists identifying flaws in arguments, and recognizing misunderstandings or points of disagreement, among the skills the Logical Reasoning section tests. It says the questions are designed to evaluate your ability to examine, analyze and critically evaluate arguments as they occur in ordinary language.
LSAC states that you will not need the meaning of specialized terms such as ad hominem or syllogism. That matches how flaw answer choices are written, which is in general descriptions of the error instead of Latin labels, so practice describing the mistake in plain words.
3 original practice questions
Written for this guide, not taken from any licensed test. Your result is saved on this device only.
All of the company's top-performing salespeople attended a particular sales training program. Therefore, requiring every salesperson to attend the program will make them top performers. The argument is flawed because it
Answer and explanations
Correct answer: B. The argument assumes the training caused top performance rather than merely correlating with it, then applies that unproven causal claim to a different population: salespeople who haven't already shown top performance. Cost and definitions are beside the point.
Councilmember: 'Our city's new curfew law must be working, since juvenile arrests are down 30% since the law took effect.' Critic: 'That's not convincing: the police department was also short-staffed for most of that period and made fewer arrests overall, for both juveniles and adults.' The critic's response does which of the following?
Answer and explanations
Correct answer: B. The critic doesn't attack the councilmember personally or deny the data: the critic supplies a competing cause, reduced policing capacity, that could produce the same drop in arrests without the curfew law being responsible.
A study found that people who take a particular vitamin supplement report fewer colds per year than people who do not. The study's authors conclude that the supplement prevents colds. This argument is most vulnerable to criticism because it
Answer and explanations
Correct answer: B. This is a self-selection confound: people who choose to take supplements may also sleep, eat, and exercise differently. Without ruling out those habits, the study can't isolate the supplement as the actual cause.
Questions this guide answers
What is an LSAT flaw question?
It asks you to name the specific logical error in an argument, usually by matching it to an abstract description in an answer choice instead of a plain label.
Which flaws come up again and again on the LSAT?
Treating correlation as causation, generalizing from an unrepresentative case, and confusing a necessary condition with a sufficient one, according to this guide's practice list.
What is necessary-for-sufficient confusion in a flaw question?
Treating a condition that is merely required as if it guarantees the outcome, such as assuming that because top performers all attended a training, attending makes anyone a top performer.
What is an unrepresentative sample flaw?
Generalizing from a small, self-selected or unusual group to a broader population that may differ in relevant ways, without showing that the group is typical.
Why do flaw answer choices not mention the topic?
They describe the error in general terms, for example presuming that a sufficient condition is also necessary, so match the description of your own plain-language error, not the nouns.
Do I need Latin names for flaws on the LSAT?
No. LSAC says you will not need specialized terms such as ad hominem or syllogism, though you must be able to understand and critique the reasoning in an argument.
How many full official practice tests are free?
LSAC says four full four-section PrepTests are free through LawHub, which lets you practice flaw questions in the actual test interface.
What does LSAC say flaw questions test?
LSAC lists identifying flaws in arguments and recognizing misunderstandings or points of disagreement among the skills tested in the Logical Reasoning section.
Your next steps
- Name the argument's flaw in your own words before reading the choices.
- Watch for correlation treated as causation: it's the single most common LSAT flaw.
- Check whether a claimed 'requirement' has been quietly treated as a 'guarantee.'
- Eliminate any choice that only restates the topic without describing an actual error.