Primary and Secondary Sources

Primary and
Secondary Sources
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Types of Evidence to Gather

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What does the Patterson's bigfoot film really show?
What about the Zapruder film of Kennedy's assassination?

Examine Evidence from the Field

Some research must be done outside the lab--examine the footprints alleged to belong to bigfoot;


Some research in done in a laboratory An experiment is typically used to test a hypothesis or theory. Replication of the results is the standard test of validity. Experimentation is a form of empirical evidence and is very prominent in sciences. (Types).

Cite the Views of

A common way of supporting a claim is to cite an authority's views on the subject you are writing about. (Types). This is a good place to start or finish.

Use Statistics

Statistical evidence is the kind of data people tend to look for first when trying to prove a point. That's not surprising when you consider how prevalent it is in today's society. Remember those McDonald's signs that said "Over 1 billion served"? How about those Trident chewing gum commercials that say "4 out of 5 dentists recommend chewing sugarless gum"? Every time you use numbers to support a main point, you're relying on statistical evidence to carry your argument. (Carmen). A primary tool for those in the natural and social sciences. It is important not to take statistics at face value, but to critically evaluate their validity. (Types).

Tell an Anecdote

Often dismissed as untrustworthy and meaningless, anecdotal evidence is one of the more underutilized types of evidence. Anecdotal evidence is evidence that is based on a person's observations of the world. It can actually be very useful for disproving generalizations because all you need is one example that contradicts a claim.
Be careful when using this type of evidence to try and support your claims. One example of a non-native English speaker who has perfect grammar does NOT prove that ALL non-native English speakers have perfect grammar. All the anecdote can do is disprove the claim that all immigrants who are non-native English speakers have terrible grammar.
You CAN use this type of evidence to support claims, though, if you use it in conjunction with other types of evidence. Personal observations can serve as wonderful examples to introduce a topic and build it up - just make sure

Of Witnesses

Testimony is the basis for our legal system. "This type of proof is used to provide the audience insight into an event/topic from someone who has direct knowledge of that event/topic. The persuasive impact of someone who has direct knowledge of a topic is often viewed as highly credible. Such testimony lends personal knowledge or insight into a topic, thus making it more real to the audience. " (Kirk). However, not all testimony is reliable.

Create an

The last type of evidence is called analogical evidence. It is also underutilized, but this time for a reason. Analogies are mainly useful when dealing with a topic that is under-researched. If you are on the cutting edge of an issue, you're the person breaking new ground. When you don't have statistics to refer to or other authorities on the matter to quote, you have to get your evidence from somewhere. Analogical evidence steps in to save the day.
Take the following example: You work for a company that is considering turning some land into a theme park. On that land there happens to be a river that your bosses think would make a great white-water rafting ride. They've called on you to assess whether or not that ride would be a good idea.
Since the land in question is as yet undeveloped, you have no casualty reports or statistics to refer to. In this case, you can look to other rivers with the same general shape to them, altitude, etc. and see if any white-water rafting casualties have occurred on those rivers. Although the rivers are different, the similarities between them should be strong enough to give credibility to your research. Realtors use the same type of analogical evidence when determining the value of a home.
When you use analogies to support your claims, always remember their power. (Carmen).
I remember attending a seminar one time sponsored by a railroad company. One of the engineers who spoke that day tried to explain why it was so important for motorists to understand the danger of trying to out run a train at a street crossing. He argued that the impact of a train traveling at 30 miles an hour hitting a car broadside was the equivalent of a car running over an empty Coke can. That illustration stuck with me for twenty years. That's powerful! (Kirk).

Works Cited for this Page
Carmen. "The Four Types of Evidence." Writing Simplified.
Kirk, Rita. "Types of Evidence Commonly Used in Speeches".
American Communication Association.
"Types of Evidence."
Colgate University Libraries.