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Evaluating Evidence To judge whether the evidence is good or bad,we ask three questions:1)Is the evidence sufficient?Is there enough of it,or do you need more to feel convinced?2)Is the evidence relevant?Is it really about the claim the author wants to prove,or did they go off on a tangent,providing facts that dont have anything to do with the claim?3)Is the evidence representative?Representative evidence accurately portrays the object of study,not distorted and not just a select piece.Another word for representative is typical.Sufficient Evidence How do you know theres enough evidence?What makes evidence sufficient to prove a claim?There is no simple answer to these questions.To a large extent its a matter of individual judgment,based on what you know about a topic,the assumptions you make,your ability to draw conclusions from the facts available.Lets say I want to prove its going to rain soon.This is my claim.For evidence,I point out that its cloudy.This might be true,but is it enough?Probably not,since its often cloudy without actually raining.Suppose I add that the barometer is dropping,the temperature is dropping,wind is picking up and the air smells“damp.”Is that enough to prove its going to rain?For many people,that would be enough to convince them that rain is coming,or at least likely.Generally speaking,of course,more evidence is better,and more types of evidence are better.In the first example above,there was just one piece of evidence(clouds)and one type(physical detail).In the second,there were four additional pieces of evidence(barometer,temperature,wind and smell),and two types(barometer and temperature are numerical evidence,while wind and smell are physical detail,although from different sensestouch and smell).You can also consider the total evidence that could be included,if one were able,and ask whether the author has provided a significant portion of that.For example,suppose I wanted to prove that Community and Technical Colleges in Washington are suffering from budget cuts,and I give examples from 15 of the 34 colleges in the state.Ive cited nearly half the entire group under discussion.For many,this would be enough to show that the colleges in general are suffering.Its usually easier to spot claims that you think do not have enough evidence than to explain why you think something does.But even when discussing insufficient evidence,try to think about what it needs:what would be“enough,”and why?Each case is different and will require its own evaluation.Dont expect to have the“right”answer,because the definition of“enough”is too subjective.Instead,think about whether the evidence feels like enough to you,and why.Think about how many separate facts or examples have been given,the different types of evidence,and the total amount of evidence that could be given if there was room.Aim for a convincing explanation of your reasons,not the“right”answer.Relevant Evidence Evidence is relevant when it has a definite relationship to the claim.The relationship does not have to be direct or clear,but it has to be there.Of course,a direct and clear relationship is preferable,but its not required.Relevance is not a binary(yes-no,either-or).Rather,it is a matter of degree.Suppose Im shopping for a used car.Ive found one Im interested in and I want to know if its a good car.The person selling it points out that it has a really nice paint job.Is this relevant?Somewhatafter all,most people would prefer a car that looks good.But its not as relevant as how well the engine runs,the condition of the transmission,or the bent frame that the paint job is trying to disguise.Relevance is probably the easiest of the three criteria to evaluate.The simplest way to do it is,if you think the evidence is relevant,to explain how it relates to the claim.If you think it is not,explain why it does not connect,or give an example that would be more relevant.Representative Evidence Representative comes from the word represent.Evidence represents,or gives us a picture of,the topic,and representative evidence gives us a complete and undistorted picture.Another word for representative is typical.Representative examples are those that are typical,or most like the majority of other items in the same group.For instance,when trying to prove the age of my students,I point to the oldest or the youngest person present.The evidence is not representative.On the other hand,if I chose a more typical student,Id be giving a better picture of the age of most of the students.For another instance,I want to prove that Americans are generous,and to prove it I point to Bill Gates.He has given away billions of dollars!Does this prove my claim?Is Gates a typical American?Nohe has tons of money to give away,and he has made that a special goal for himself.Therefore,he does not represent Americans in general.He is not the best example.A much better example would be an ordinary working person who makes an average income,because such a person is more likely to represent a typical American.Representative of what?When deciding if a piece or a collection of evidence is representative,it is crucial to ask what it is trying to represent.“Representative of what?”should be the first question you ask.To look at the Bill Gates example again,we might ask,is he supposed to represent Americans income or their attitude toward giving?He is clearly not representative when it comes to income,but he might be representative of Americans attitude about giving.Maybe most Americans would do the same if they had his money.My point here is not that Bill Gates is typical in this regard,but to point out that an example can be either representative or unrepresentative,depending on what you think its supposed to represent.That is why it is essential to ask,“representative of what?”To Sum Up When evaluating an arguments evidence,you ask three questions:Is it sufficient?Is it relevant?Is it representative?In each case you must give your reasons.Acknowledgements to David Oldham The article above is adapted from his writing about Evidence on