# Do Percentages Always Work?
**URL:** https://boards.straightdope.com/t/do-percentages-always-work/150771
**Category:** Factual Questions
**Created:** [January 25, 2003, 12:59am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771 "2003-01-25T00:59:44Z")
**Posts on this page:** 19
**Page:** 1
### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [January 25, 2003, 12:59am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/1 "2003-01-25T00:59:44Z")
I was wondering: If something fails on its first try, we’d say it has a 100% failure rate. But, if it fails on the second try, we still say it has a 100% failure rate. But, I argue…shouldn’t this really be a 200% failure rate? How come there is no accounting for this when we work with percentages (other than, say a price hike of 200%)?
Just thinking outside the box, or cage on the funny farm. OK, I’ll go back to my cage now! 😃 - Jinx
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [January 25, 2003, 1:07am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/2 "2003-01-25T01:07:44Z")
You can’t have 200% of something without increasing the amount of something; it would be absurd to say that 200% of cats have breath that smells of cat food.
Anyway, is this about Cecil’s divorce frequency column?
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [January 25, 2003, 1:09am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/3 "2003-01-25T01:09:41Z")
If something fails on the first try all the time, it has a 100% first-time failure rate; if, in half of all instances, it fails on the second time (the other half still failing on the first), then it has a 50% first-time failure rate and 100% rate of failure across two ‘tries’
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### Author:  [@Scupper](https://boards.straightdope.com/u/Scupper)
#### Post date: [January 25, 2003, 1:10am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/4 "2003-01-25T01:10:32Z")
Percent means “out of 100.” You can’t fail more than 100 times in 100 tries, no matter how hard you try.
The number of attempts has increased 100% (if you try once more and fail, you will have increased the number of tries by 200% total), but the failure rate is still 2 out of 2, or 100%.
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### Author:  [@Shade](https://boards.straightdope.com/u/Shade)
#### Post date: [January 25, 2003, 1:12am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/5 "2003-01-25T01:12:08Z")
Let me take a stab: 0% means ‘none of it;’ 100% means ‘all of it;’ 200% means ‘two lots of it.’
So a 100% failure rate means ‘all of the attempts have been failures.’ (‘rate’ here means expressed compared to the total.)
If you mean ‘failed twice as often’ you could say ‘there are now 200% failed experiments (compared to before)’
Percentages are FOR giving somthing compared to the total. If you want to do something else you use something else, (or choose a stupid thing to take percentages compared to.)
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### Author:  [@Lobsang](https://boards.straightdope.com/u/Lobsang)
#### Post date: [January 25, 2003, 1:53am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/6 "2003-01-25T01:53:40Z")
wasbla meem! bloogleflob, smelb worblyflarm!
(ask silly questions and…)
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### Author:  [@brad\_d](https://boards.straightdope.com/u/brad_d)
#### Post date: [January 25, 2003, 3:20am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/7 "2003-01-25T03:20:35Z")
In the example you give, a 200% failure rate would suggest that the product failed two times for every one attempt (2/1 = 2 = 200%).
Never mind trying to decide what that means - it’s not what happened here. The product failed two times in _two_ attempts.
The failure rate is (failures) / (total tries). 2/2 = 1 = 100%.
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### Author:  [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)
#### Post date: [January 25, 2003, 4:04am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/8 "2003-01-25T04:04:15Z")
> [@](#):
>
> \*Originally posted by Scupper \*
> **Percent means “out of 100.” You can’t fail more than 100 times in 100 tries, no matter how hard you try.**
Yeah, if the OP wants to get technical about it, they should wait until they’ve had a hundred failures before calculating a percentage. Solves that problem.
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### Author:  [@Urban\_Ranger](https://boards.straightdope.com/u/Urban_Ranger)
#### Post date: [January 25, 2003, 5:28am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/9 "2003-01-25T05:28:44Z")
[QUOTE]
\*Originally posted by Jinx \*
I was wondering: If something fails on its first try, we’d say it has a 100% failure rate. /QUOTE]
Shouldn’t be 50%?
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### Author:  [@samarm](https://boards.straightdope.com/u/samarm)
#### Post date: [January 25, 2003, 6:01am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/10 "2003-01-25T06:01:07Z")
No, it should be 100%.
Something fails on it’s first try: It was tried 1 time. It failed 1 time. 100% failure rate.
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### Author:  [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)
#### Post date: [January 25, 2003, 2:57pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/11 "2003-01-25T14:57:26Z")
> [@](#):
>
> \*Originally posted by RM Mentock \*
> **they should wait until they’ve had a hundred failures**
I meant, a hundred tries. Of course. 🙂
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### Author:  [@Cooper](https://boards.straightdope.com/u/Cooper)
#### Post date: [January 25, 2003, 4:06pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/12 "2003-01-25T16:06:06Z")
I thought the OP was asking shouldn’t there be a way to show the number of trials - or maybe our confidence in the percentage. Well, percentages are really too simple for that. Statistics is a lot more than just percentages, and there are standard notations for showing sample sizes as well as confidence. You may have seen a simplification of this in a magazine where they tell you the margin of error for a telephone poll for example…there are specific ways of calculating the margin of error and it in part depends upon the sample size.
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### Author:  [@SandWriter](https://boards.straightdope.com/u/SandWriter)
#### Post date: [January 25, 2003, 5:34pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/13 "2003-01-25T17:34:36Z")
> [@](#):
>
> \*Originally said by Mark Twain \*
> **There’s lies, Damn lies, and statistics!**
dood, when someone starts talking about percentages, my ears go up. Why talk in percentages when you can use ‘real’ numbers?
oh, and scupper, that’s not true. you can have fractions of a percent, so if you have a lot of 1000 light bulbs, and 1 doesn’t work, then the lot is considered 99.90% functional.
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### Author:  [@Gary\_T](https://boards.straightdope.com/u/Gary_T)
#### Post date: [January 25, 2003, 7:30pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/14 "2003-01-25T19:30:25Z")
_if it fails on the second try, we still say it has a 100% failure rate. But, I argue…shouldn’t this really be a 200% failure rate?_
No, because it didn’t fail twice as often as it was attempted (which would of course be impossible). It has failed 100% (all) of the times it was tried. If there had been success on the second try, the failure rate **FOR THE TWO ATTEMPTS** would be 50%.
Here’s the key concept I think you’re overlooking: **When you add an additional attempt, you change the number of things you’re taking a percentage of.**
Try once, fail once, 100% failure rate.
Try twice, fail twice, 100% failure rate.
Try twice, fail once, 50% failure rate.
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### Author:  [@CC](https://boards.straightdope.com/u/CC)
#### Post date: [January 25, 2003, 8:16pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/15 "2003-01-25T20:16:31Z")
On the other hand, since this has been explained over and over pretty much the same way, you have about 500% of the answers you need.
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### Author:  [@kniz](https://boards.straightdope.com/u/kniz)
#### Post date: [January 25, 2003, 9:46pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/16 "2003-01-25T21:46:58Z")
[sup]Remember my post in the other thread? It really does apply here.[/sup]
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### Author:  [@SandWriter](https://boards.straightdope.com/u/SandWriter)
#### Post date: [January 26, 2003, 2:34am UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/17 "2003-01-26T02:34:12Z")
I agree, he’s scraping the bottom of the…keyboard?
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### Author:  [@handy](https://boards.straightdope.com/u/handy)
#### Post date: [January 26, 2003, 4:30pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/18 "2003-01-26T16:30:26Z")
Ah, one of my favorite books & still sold, ‘How to lie with statistics’…
you might like it Jinx.
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### Author:  [@sailor](https://boards.straightdope.com/u/sailor)
#### Post date: [January 26, 2003, 4:41pm UTC](https://boards.straightdope.com/t/do-percentages-always-work/150771/19 "2003-01-26T16:41:53Z")
Don’t they teach anything in school any more? This stuff is just so basic. . .