Dr. Tamara Fudge, Kaplan University professor in the School of Business and IT
There are several ways to present information when writing, including those that employ inductive and deductivereasoning. The difference can be stated simply:
- Inductive reasoning presents facts and then wraps them up with a conclusion.
- Deductive reasoning presents a thesis statement and then provides supportive facts or examples.
Which should the writer use? It depends on content, the intended audience, and your overall purpose.
If you want your audience to discover new thingswith you, then inductive writing might make sense. Here is n example:
My dog Max wants to chase every non-human living creature he sees, whether it is the cats in the house or rabbits and squirrels in the backyard. Sources indicate that this is a behavior typical of Jack Russell terriers. While Max is a mixed breed dog, he is approximately the same size and has many of the typical markings of a Jack Russell. From these facts along with his behaviors, we surmise that Max is indeed at least part Jack Russell terrier.
Within that short paragraph, you learned about Max’s manners and a little about what he might look like, and then the concluding sentence connected these ideas together. This kind of writing often keeps the reader’s attention, as he or she must read all the pieces of the puzzle before they are connected.
Purposes for this kind of writing include creative writing and perhaps some persuasive essays, although much academic work is done in deductive form.
If your audience is not likely going to read the entire written piece, then deductive reasoning might make more sense, as the reader can look for what he or she wants by quickly scanning first sentences of each paragraph. Here is an example:
My backyard is in dire need of cleaning and new landscaping. The Kentucky bluegrass that was planted there five years ago has been all but replaced by Creeping Charlie, a particularly invasive weed. The stone steps leading to the house are in some disrepair, and there are some slats missing from the fence. Perennials were planted three years ago, but the moles and rabbits destroyed many of the bulbs, so we no longer have flowers in the spring.
The reader knows from the very first sentence that the backyard is a mess! This paragraph could have ended with a clarifying conclusion sentence; while it might be considered redundant to do so, the scientific community tends to work through deductive reasoning by providing (1) a premise or argument – which could also be called a thesis statement, (2) then evidence to support the premise, and (3) finally the conclusion.
Purposes for this kind of writing include business letters and project documents, where the client is more likely to skim the work for generalities or to hunt for only the parts that are important to him or her. Again, scientific writing tends to follow this format as well, and research papers greatly benefit from deductive writing.
Whether one method or another is chosen, there are some other important considerations. First, it is important that the facts/evidence be true. Perform research carefully and from appropriate sources; make sure ideas are cited properly. You might need to avoid absolute words such as “always,” “never,” and “only,” because they exclude any anomalies. Try not to write questions: the writer’s job is to provide answers instead. Lastly, avoid quotes in thesis statements or conclusions, because they are not your own words – and thus undermine your authority as the paper writer.
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The term "inductive reasoning" refers to reasoning that takes specific information and makes a broader generalization that is considered probable, allowing for the fact that the conclusion may not be accurate.
Understanding Inductive Reasoning
There are varying degrees of strength and weakness in inductive reasoning, and various types including statistical syllogism, arguments from example, causal inferences, simple inductions, and inductive generalizations. They can have part to whole relations, extrapolations, or predictions.
Some examples of inductive reasoning include:
- Jennifer leaves for school at 7:00 a.m. Jennifer is always on time. Jennifer assumes, then, that she will always be on time if she leaves at 7:00 a.m.
- The cost of goods was $1.00. The cost of labor to manufacture the time was $.50. The sales price of the item was $5.00; so, the item always provides a good profit.
- Every windstorm in this area comes from the north. I can see a big cloud of dust caused by a windstorm in the distance; so, a new windstorm is coming from the north.
- Bob is showing a big diamond ring to his friend Larry. Bob has told Larry that he is going to marry Joan. Bob has bought the diamond ring to give to Joan.
- The chair in the living room is red. The chair in the dining room is red. The chair in the bedrrom is red. All chairs in the house are red.
- Every time you eat peanuts, your throat sweels up and you can't breath. So, you are allergic to peanuts.
- All cats that you have observed purr. Therefore, every cat must purr.
- Two-thirds of the students at this college receive student aid. Therefore, two-thirds of all college students receive student aid.
- All of the girls in the class were blond, therefore all girls in this neighborhood are blond.
- Michael just moved here from Chicago. Michael has red hair, therefore people from Chicago have red hair.
- The children in that house yell loudly when they play in their bedroom. I can hear children yelling in that house, therefore the children must nbe playing in their bedroom.
- All chickens that we have seen have been brown; so, all chickens are brown.
- All cars in this town drive on the right side of the street. Therefore, all cars in all towns drive on the right side of the street.
- John is an excellent swimmer. John's family has a swimming pool. John's sister Mary must also be an excellent swimmer.
- All basketball players in your school are tall, so all basketball players must be tall.
- All brown dogs in the park are small dogs. Therefore, all small dogs are brown.
- All children in the day care center like to play with Legos. All children, therefore, enjoy playing with Legos.
- Ray is a football player. All football players weigh more than 170 pounds. Ray weighs more than 170 pounds.
- All observed houses on the South Street are falling apart. Sherry lives on South Street. Her house is falling apart.
Now you can see how inductive reasoning works and the types of things you can discern using inductive reasoning.