©2007 by The McGraw-Hill Companies, Inc. All rights reserved.

Assessing a Claim’s Initial Plausibility

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The aim of this tutorial is to help you learn to assess a claim’s initial

plausibility.

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©2007 by The McGraw-Hill Companies, Inc. All rights reserved.

When we read or hear a new informative claim, how do we decide whether or not to believe it?

Even if there are not any arguments provided for the claim, it is generally reasonable to accept the claim if it does not conflict with our store of background information and if it comes from a reliable source.

A claim’s initial plausibility is a measure of how well it "squares" with our background information and our own observations.

Decide whether each of the following claims has initial plausibility. If not, decide whether they conflict more with

observations or with background information.

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©2007 by The McGraw-Hill Companies, Inc. All rights reserved.

Your kids will grow faster with two ginseng supplements a day.

To assess the initial plausibility of this claim you must measure it against observations you have made and your background information about children, growth, and supplements.

Based on these considerations how plausible is it that this claim is true?

This claim does not have much initial plausibility. Both observations and what we know about biology suggest

that growth rates are not affected by supplements.

Of course, your own observations or background information may tell you different.

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©2007 by The McGraw-Hill Companies, Inc. All rights reserved.

Vomiting is your body’s way of getting rid of something harmful.

Measure this claim against your own observations as well as your general store of background information.

Based on these considerations how plausible is it that this claim is true?

People often vomit after eating spoiled food or after drinking too much alcohol. This claim fits with this background information.

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On the other hand, amusement park rides and even car trips cause people to vomit, too. This observation contradicts the claim.

This claim has some initial plausibility.

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©2007 by The McGraw-Hill Companies, Inc. All rights reserved.

If your gas gauge says “E,” you have two gallons left in the tank.

Measure this claim against your own observations as well as your general store of background information.

Based on these considerations how plausible is it that this claim is true?

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This claim has a fairly strong initial plausibility.

This claim seems to fit well with many driving experiences. It also seems to coincide with background information about manufacturers adding a margin of error in their tanks.

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©2007 by The McGraw-Hill Companies, Inc. All rights reserved.

Cold weather alone does not make someone catch a cold.

Measure this claim against your own observations as well as your general store of background information.

Based on these considerations how plausible is it that this claim is true?

Observations tell you that most colds come during the winter and not the summer and the claim seems to contradict this.

This is the end of the tutorial.

On the other hand, we know that colds are caused by viruses and not by temperature alone.

This claim has mixed, but all in all, fairly strong initial plausibility.

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