My last two articles (part 1 and part 2) gave you some advanced tools to analyze deductive reasoning. Now it’s time to dive into the wonderful world of inductive reasoning, which appears much more often, especially in the following GMAT question types:
• Fill in the blank
• Identify the role
• Identify the overall reasoning
• Identify the conclusion
• Mimic the reasoning (sometimes)
According to Wikipedia:
“Inductive reasoning (as opposed to deductive reasoning) is reasoning in which the premises seek to supply strong evidence for (not absolute proof of) the truth of the conclusion. While the conclusion of a deductive argument is supposed to be certain, the truth of an inductive argument is supposed to be probable, based upon the evidence given.”
Therefore, in inductive arguments, conclusions are a matter of opinion, some more strongly supported than others.
Beyond the basics: P.O.S.E.
First, from class and your own study, you should be able to DECONSTRUCT arguments–in other words, identify the background, conclusion, premises, counterpoint, and counter premises of all inductive arguments. Our books cover that skill thoroughly if you need more work.
Next, you should learn to categorize each conclusion by type.
Fortunately, the GMAT uses only a few basic argument patterns, with similar assumptions and a limited number of ways to strengthen or weaken those assumptions. If you can spot and name those patterns, you’re well on your way to drastically improving your CR score.
I combed through every available CR question I could find, and discovered that the GMAT only writes 4 types of conclusions: predictions, opinions, solutions, and explanations (acronym P.O.S.E.)
Predictions: Something that “will” happen sometime in the future, using past or present circumstances to make that prediction.
Opinions: Interpretations of facts or data–often value judgments (good/bad/true false). I use “opinion” as a catchall category for anything that doesn’t fall under the other three.
Solutions: Plans, recommendations, solutions to problems, strategies, or suggestions of what someone “should” or “must” do.
Explanations: WHY something happened, or the cause of some phenomenon.
In future articles, I’ll divide the pie even more, showing you how the GMAT uses logical fallacies so common that they have Latin names, but for now let’s just stick to the big four.
The following are conclusions quoted from The Official Guide for GMAT Review 13th Edition, by GMAC®, questions 27 – 42. Name the TYPE. Is it a solution, prediction or explanation? If you can’t name it as one of those three, just call it an opinion for now. If you want more information, open your book and look at the whole argument, including the question stem. Write down your ideas before you look at mine.
27. “Clearly, therefore, insurance companies are making a greater profit on collision-damage insurance in Greatport than in Fairmmont.”
28. “Clearly, it can be concluded that the number of new jobs created this year will fall short of last years record.”
29. “The government ministry plans to reassure worried gardeners by…”
30. “To help track the ruffle’s spread, government agencies have produced wallet-sized cards about the ruffle.”
31. “This fact, however, does not indicate that most chickens are immune to the virus…”
32. “We can conclude that inflation is on an upward trend and the rate will still be higher next year. ”
33. “This proposal, however, is ill conceived.”
34. “…for economic reasons alone the board should be disbanded.”
35. “Thus, the loss to the industry is quite small…”
36. “That assumption, however, is evidently false.”
37. “Therefore, the decrease in coffee consumption must have been caused by consumer’s awareness of the harmful effects of coffee.”
38. “It should be expected that…”
39. “Thus, Sviatovin must have been written between 1165 and 1167…”
40. “The Mooreville Transit authority plans to…Officials predict that…”
41. “Therefore, by installing scrubbers, Northern Power will be doing the most that can be done…”
42. “Therefore, to reduce shipping time, Trancorp plans to switch to trains…”
Answers: (If you saw something different, let me know in the comments section, and we can debate!)
27. Opinion (interpretation of studies)
29. Solution/Plan. Check out the word “plan” in the question, too!
30. Solution/Plan. Check out the word “action” in the question…
31. Opinion. If you said explanation, I’ll accept that.
32. Prediction. The word “will” is a big hint.
33. Solution (or rejection of a solution). “Proposal” is usually some kind of solution or recommendation.
37. Explanation! The words “caused by” are a big hint.
40. Solution (“plans to”) AND prediction.
41. Opinion. Not quite a prediction of the future, despite the word “will.”
How’d you do? You can do this exercise with the WHOLE official guide in less than an hour. I highly recommend it!
Wouldn’t it be nice, on the real GMAT, to see a dozen arguments you’ve seen a hundred times already? Similar conclusions have similar assumptions. And similar assumptions have similar ways to strengthen, weaken, and evaluate. If you can categorize using P.O.S.E, you can answer everything faster and more accurately.
ANALYSIS WITH REAL GMAT QUESTIONS
Here are the basics of how to analyze and answer using P.O.S.E.:
As I said before, every inductive conclusion is an opinion. Therefore, I’m going to start here. The generic pattern is as follows:
Conclusion: Opinion, interpretation, declarative statement, or judgment call.
Premises: Facts, information, data, statistics, circumstances, etc.
Assumptions: The author is assuming that the facts are RELEVANT to his or her conclusion, the facts are SUFFICIENT to prove the conclusion (with a high probability), and there are NO OTHER FACTORS that would decrease the probability of the conclusion.
Strengthen: Add factual evidence that increases the probability of the conclusion. Conversely, you can remove/disprove a factor that would decrease the probability of the conclusion.
Weaken: Add evidence (another factor) that decreases the probability of the conclusion.
GMAT example: Art’s Decline from GMATPrep® practice test software.
Reviewer: The book Art’s Decline argues that European painters today lack skills that were common among European painters of preceding centuries. In this the book must be right, since its analysis of 100 paintings, 50 old and 50 contemporary, demonstrates convincingly that none of the contemporary paintings are executed as skillfully as the older paintings.
Which of the following points to the most serious logical flaw in the reviewer’s argument?
(A) The paintings chosen by the book’s author for analysis could be those that most support the book’s thesis.
(B) There could be criteria other than the technical skill of the artist by which to evaluate a painting.
(C) The title of the book could cause readers to accept the book’s thesis even before they read the analysis of the paintings that supports it.
(D) The particular methods currently used by European painters could require less artistic skill than do methods used by painters in other parts of the world.
(E) A reader who was not familiar with the language of art criticism might not be convinced by the book’s analysis of the 100 paintings.
Some LSAT teachers might call this a “flaw” question, but since the correct answer will attack the conclusion, you can just call it a “weaken” question.
Conclusion: “In this [painters today lack skills] the book must be right.”
Notice how this is more of a value judgment than a prediction, explanation, or solution, so we can just call it a general “opinion.”
Premise: In the 100 paintings in the book, the 50 old ones were more skilled than the 50 contemporary.
With any opinion, ask yourself the following questions:
Are the premises RELEVANT? Are these 100 paintings representative of ALL old and contemporary paintings?
Are the premises SUFFICIENT? Are 100 paintings enough to prove a blanket statement about all European artists?
Could there be OTHER FACTORS? Are there other paintings not in the book that might disprove this conclusion?
3) State the goal:
We need to find an answer that proves these 100 paintings are irrelevant/unrepresentative, or that there’s another factor that makes contemporary painters just as skilled, if not more skilled, than the old ones.
4) POE (Process Of Elimination)
The correct answer (A) indicates that the paintings might have been selected to prove the thesis (an unrepresentative sample), and suggests there may be other paintings that disprove the conclusion.
Key words: predict, will, probably, future, trend, etc.
Conclusion: Something “will” happen in the future.
Premises: A description of past events, or a description of the present.
Assumptions: The past (or present) is the same as the future, with no significant differences. Nothing will change to affect the future.
To strengthen: Show that nothing will change, that trends occurring in the present will continue in the same direction.
To weaken: Show that something significant is going to change.
GMAT Example: Gortland from GMATPrep® practice test software.
Gortland has long been narrowly self-sufficient in both grain and meat. However, as per capita income in Gortland has risen toward the world average, per capita consumption of meat has also risen toward the world average, and it takes several pounds of grain to produce one pound of meat. Therefore, since per capita income continues to rise, whereas domestic grain production will not increase, Gortland will soon have to import either grain or meat or both.
Which of the following is an assumption on which the argument depends?
(A)The total acreage devoted to grain production in Gortland will soon decrease.
(B)Importing either grain or meat will not result in a significantly higher percentage of Gortlands’ incomes being spent on food that is currently the case.
(C)The per capita consumption of meat in Gortland is increasing at roughly the same rate across all income levels.
(D)The per capita income of meat producers in Gortland is rising faster than the per capita income of grain producers.
(E) People in Gortland who increase their consumption of meat will not radically decrease their consumption of grain.
First of all, this is an assumption question. The answer will support the argument. In fact, the argument won’t hold up without this assumption.
Conclusion: “Gortland will soon have to import grain or meat or both.”
AHA! The word “will” indicates the author is making a prediction.
Predictions often make the assumption that nothing else will change. We know consumption of meat is in the rise, so the author is assuming that consumption of grain will stay the same.
3) State the goal:
I predict that the answer will say something to the effect of “nothing else changes.”
4) POE (Process Of Elimination)
The only two answers that imply, “things WON’T change” are (B) and (E). But (B) mentions income, which is irrelevant to the prediction. And if people did decrease their grain consumption, the conclusion would fall apart. (E) must be the answer.
(By the way, I plan a whole future article on causal/correlation flaws, so this is just an intro.)
Key words: due to, result of, cause, because, reason why, etc.
Conclusion: Event A caused Event B (causation).
Premises: Event A occurred. Event B also occurred (correlation).
Assumptions: Event A is the only cause. There are no other causes. Event B did not cause event A (not reversed). It’s not a coincidence.
To strengthen: Provide evidence for a causal link. Eliminate potential other causes. Show that the purported cause happened first (and very close in time). With a control group, show what happens when you remove the proposed cause (no cause = the effect should go away).
To weaken: Show evidence another cause. Prove it was a coincidence. Show the cause without the effect. Show the effect without the cause. Show that B was actually the cause of A.
GMAT Example: Sea Otters from GMATPrep® practice test software.
In the late 1980s, the population of sea otters in the North Pacific began to decline. There are two plausible explanations for the decline: predation, possibly by killer whales, or disease. Of these two, disease is the more likely, since a concurrent sharp decline in populations of seals and sea lions is believed to have been caused by disease, and diseases that infect these creatures are likely to be able to infect sea otters also.
Which of the following, if true, most seriously weakens the reasoning?
(A) Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.
(B) There is no indication that the sea otter population at any North Pacific location declined in the 1980s because of substantial numbers of sea otters migrating to other locations.
(C) Along the Pacific coast of North America in the 1980s, sea otters were absent from many locations where they had been relatively common in former times.
(D) Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters’ main food source.
(E) The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.
This is a weaken question. The answer will provide evidence against the conclusion.
“There are two possible explanations […] Of these two, disease is more likely.”
Hey! Looks like we have an “explanation” argument.
In this case, we need to weaken the explanation of disease. The best way to weaken an explanation is to provide evidence of alternative cause–in this case, killer whales.
3) State the goal.
We’re looking for an answer that suggests killer whales are killing the otters.
The only answer that even mentions killer whales is (A). And if seals and sea lions are dying of disease, then the killer whales will be going after other food, namely the otters! The answer must be (A).
Key words: plan, strategy, proposal, policy, solution, recommendation, action, must, should, profit, etc.
Conclusion: Solution, Plan, or recommendation.
Premises: Problem or situation that need to be improved. Reasons the plan will work.
Assumptions: The solution is effective and complete. It will actually work to cure causes of the problem. The benefits of the solution outweigh the costs, downsides, and side effects. The solution won’t be worse than the problem itself.
To Strengthen: Provide evidence that support the above assumptions.
To Weaken: Show that the costs or side effects outweigh the benefits. Prove the solution is ineffective or incomplete.
GMAT Example: Seaweed solution from GMATPrep® practice test software.
Scientists are discussing ways to remove excess carbon dioxide from the atmosphere by increasing the amount that is absorbed by plant life. One plan to accomplish this is to establish giant floating seaweed farms in the oceans. When the seaweed plants die, they will be disposed of by being burned for fuel.
Which of the following, if true, would indicate the most serious weakness in the plan above?
(A) Some areas of ocean in the Southern Hemisphere do not contain sufficient nutrients to support large seaweed farms.
(B) When a seaweed plant is burned, it releases an amount of carbon dioxide comparable to the amount it has absorbed in its lifetime.
(C) Even if seaweed farms prove effective, some people will be reluctant to switch to this new fuel.
(D) Each year about seven billion tons of carbon dioxide are released into the atmosphere but only about five billion tons are absorbed by plant life.
(E) Seaweed farms would make more money by farming seaweed to sell as nutritional supplements than by farming seaweed to sell as fuel.
This is a weaken question. The answer will provide evidence against the conclusion.
“One plan to accomplish this is to establish giant seaweed farms… ”
The word “plan” tells us we have a “solution” argument.
Problem: excess carbon dioxide.
Solution: giant floating seaweed farms to absorb carbon dioxide.
Whenever you’re confronted with a plan or solution, you have to weigh the benefits of the plan against the costs, side effects, and potential downsides.
To weaken a plan, you need to suggest that there’s an unconsidered BAD thing about the plan…
3) State the goal.
We’re looking for an answer that says the seaweed farms are a BAD idea for some reason, especially related to CO2…
(A) This seems to suggest that the plan won’t work in some places. This weakens a little, but not enough. We can just put the seaweed farms in a place where they will grow.
(B) HEY! This suggests that burning the plants will release ALL the C02 back into the atmosphere, a serious drawback to the plan to reduce CO2.
(D) This, in a way, actually strengthens the argument…
Looks like (B) shows a big negative side effect of the plan. This must be the answer.
Try this on your own with 100 more GMAT examples, especially ones you’ve gotten wrong in the past. Keep track of ways the GMAT likes to strengthen and weaken each type of P.O.S.E conclusion–you’re almost guaranteed to see it again.
Have fun! See you in the land of formal fallacies next!
* The text excerpted above from The Official Guide for GMAT Review 13th Edition is copyright GMAC® (the Graduate Management Admissions Council). The short excerpts are quoted under fair-use statutes for scholarly or journalistic work; use of these excerpts does not imply endorsement of this article by GMAC.
* GMATPrep® questions courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.