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Logical fallacy of the week

bluesteel
Posts: 12,301
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1/22/2015 4:41:40 AM
Posted: 1 year ago
Base rate fallacy.

The base rate fallacy obscures the actual magnitude of an effect by referring only to relative terms, not to absolute terms.

For example, on a topic about drones, someone might say that when the US switched to using drones in Yemen, it increased the number of civilian casualties by 8000%. What they're not telling you is the base rate: how many casualties were there before we used drones? Because the US never had any significant presence in Yemen before using drones, there were only 5 civilian casualties over the last 10 years due to one bombing run the US did with a normal airplane. When the US started using drones, they killed 400 civilians. That's an 8000% increase.

The problem is 8000% sounds like a big deal, until you know the base rate. Four hundred civilian deaths is nothing to sneeze at and ignore, but it also is far less likely to outweigh the lives saved from killing dangerous terrorists like Anwar al Awlaki (who was dubbed the next bin Laden, but on steroids). So anyway, be aware of base rate fallacy as a debater.

The proper way to point it out is not to cry "fallacy, fallacy!" Because the failure to give the base rate does not automatically invalidate the argument. The proper thing to do is go research the base rate yourself and see if it changes anything (e.g. is it ridiculously small). If it is, tell the judges what the base rate is.

*This has been a weekly presentation of Logical Fallacy of the Week. I will try to keep this series going, or get someone else to write next week's.

**All numbers and facts regarding Yemen are made up, including the fact that it is a real country.
You can't reason someone out of a position they didn't reason themselves into - Jonathan Swift (paraphrase)
The-Voice-of-Truth
Posts: 6,542
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1/22/2015 7:13:23 AM
Posted: 1 year ago
At 1/22/2015 4:41:40 AM, bluesteel wrote:
Base rate fallacy.

The base rate fallacy obscures the actual magnitude of an effect by referring only to relative terms, not to absolute terms.

For example, on a topic about drones, someone might say that when the US switched to using drones in Yemen, it increased the number of civilian casualties by 8000%. What they're not telling you is the base rate: how many casualties were there before we used drones? Because the US never had any significant presence in Yemen before using drones, there were only 5 civilian casualties over the last 10 years due to one bombing run the US did with a normal airplane. When the US started using drones, they killed 400 civilians. That's an 8000% increase.

The problem is 8000% sounds like a big deal, until you know the base rate. Four hundred civilian deaths is nothing to sneeze at and ignore, but it also is far less likely to outweigh the lives saved from killing dangerous terrorists like Anwar al Awlaki (who was dubbed the next bin Laden, but on steroids). So anyway, be aware of base rate fallacy as a debater.

The proper way to point it out is not to cry "fallacy, fallacy!" Because the failure to give the base rate does not automatically invalidate the argument. The proper thing to do is go research the base rate yourself and see if it changes anything (e.g. is it ridiculously small). If it is, tell the judges what the base rate is.

*This has been a weekly presentation of Logical Fallacy of the Week. I will try to keep this series going, or get someone else to write next week's.

**All numbers and facts regarding Yemen are made up, including the fact that it is a real country.

Next week, you should do the "Non Sequitur" fallacy.
Suh dude

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I'm Rick Harrison and this is my pawn shop. I work here with my old man and my son, Big Hoss, and in 23 years I've learned one thing. You never know what is gonna come through that door.
bluesteel
Posts: 12,301
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1/22/2015 7:24:52 AM
Posted: 1 year ago
At 1/22/2015 6:35:01 AM, Smithereens wrote:
why is 'actual magnitude,' not a relative concept?

The magnitude of an increase or a decrease is a relative concept, but "relative to what" is also an important consideration.

I could have worded that better. You get what I meant though now....

Example:

Premise: NASA has enough money. They don't need an increase in funding.

Proof: NASA's budget was increased by 300% the last fiscal year.

Fallacy: "Enough" is a concept where the base rate is important. A 300% increase in an already ridiculously small budget may not be sufficient.
You can't reason someone out of a position they didn't reason themselves into - Jonathan Swift (paraphrase)
Geographia
Posts: 1,467
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1/22/2015 10:10:50 AM
Posted: 1 year ago
At 1/22/2015 7:24:52 AM, bluesteel wrote:
At 1/22/2015 6:35:01 AM, Smithereens wrote:
why is 'actual magnitude,' not a relative concept?

The magnitude of an increase or a decrease is a relative concept, but "relative to what" is also an important consideration.

I could have worded that better. You get what I meant though now....

Example:

Premise: NASA has enough money. They don't need an increase in funding.

Proof: NASA's budget was increased by 300% the last fiscal year.

Fallacy: "Enough" is a concept where the base rate is important. A 300% increase in an already ridiculously small budget may not be sufficient.

Mah nigga. Take the Money from the military