Evaluating evidence

Creating an atmosphere of discovery by allowing visitors to evaluate evidence.


You want to explain a multi-faceted problem and have visitors evaluate the evidence.


Develop a series of web pages, on which they are directed to note their opinion about each piece of evidence and analyze the problem.

If, for example, your site is exploring unusual cancer rates in a community near a chemical factory, introduce the history of the factory and the local community, the nature of the pollution from the factory, and the limitations of different kinds of evidence. These are the degrees of certainty:

Very certain: There is abundant, compelling evidence, and only one reasonable interpretation.

Probably sure: The evidence is very strong, and you can presume an opinion, but another interpretation might be possible.

It proves nothing: The evidence is consistent with the pollution causing disease, but we are speculating and this permissive evidence cannot prove anything.

Present the visitor with a series of pages, on which they are directed to note their opinion about each piece of evidence, and note how certain they are about their conclusion. For each piece of evidence, explain the basis for the evidence, and provide an unbiased explanation of what the evidence means. Alongside every page, show the following options, under a heading, “What is your analysis?” The visitor can click buttons.

This evidence suggests the pollution caused the diseases: Yes; Not sure; No; Undecided

How conclusive is this evidence? Very certain; Somewhat sure; It proves nothing; Undecided

As the visitor clicks through the pages, a dial on the top of the page dynamically adjusts. The dial, labeled “Your Conclusion” has a range of positions, from “Caused” to “Undecided” to “Didn’t Cause.”

On a “Your Conclusion” page, total the pro and con votes. Some votes are “Very Certain,” some are “Probably Sure” and some are “It Proves Nothing.” Add the votes and calculate the overall determination.


Allowing visitors to evaluate the evidence themselves creates an atmosphere of discovery. At the end of the experience, tell visitors what the “experts” have concluded. In any good story, the experts often have widely differing opinions.

A related version of this technique is to present the visitor with a series of hypotheses, and the evidence to evaluate them. For example, what disease does a patient suffer? What caused the Space Shuttle Columbia to explode in 2003? Why did the dinosaurs become extinct? For every hypothesis, present the visitor with evidence to review, and keep track of their replies. After evaluating every hypothesis, the web site tells them which hypothesis the visitor thinks is most probable.

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