To produce a deviation as large as the one we are discussing here, a systematic bias is clearly needed.
No it isn't. You cannot expect a non-deviant result from a self-selected sample. Stop trying to insist otherwise. This is mathematical fact, not a matter of opinion.
So, I went and had a look at some statistics texts, and here are a few juicy quotes (emphasis mine):
---
Self-selection bias is the problem that very often results when survey respondents are allowed to decide entirely for themselves whether or not they want to participate in a survey. To the extent that respondents' propensity for participating in the study is correlated with the substantive topic the researchers are trying to study, there will be self-selection bias in the resulting data.
---
A voluntary response sample consists of people who choose themselves by responding to a general appeal. Voluntary response samples are biased because people with strong opinions, especially negative opinions, are most likely to respond.
---
A sample of convenience is a sample that is not drawn by a well-defined random method. The big problem with samples of convenience is that they may differ systematically in some way from the population. For this reason, samples of convenience should not be used, except in situations where it is not feasible to draw a random sample. When it is necessary to draw a sample of convenience, it is important to think carefully about all the ways in which the sample might differ systematically from the population. If it is reasonable to believe that no important systematic difference exists, then it may be acceptable to treat the sample of convenience as if it were a simple random sample.
---
Now, I've done as you asked, and in return, I would be very grateful if you would respond to my thought experiment from the other thread. I'm really quite pleased with it. I'll repeat it here, for you convenience:
So, thought experiment time:
You have a thousand people, all of which have a coin. You then ask anyone who feels like it to come forward, and flip their coin. I would expect roughly the same number of heads and tails, but would you? Remember, this is one of those scary self-selected samples.
Next, you have a thousand people, all of which have a coin. You tell them all to flip their coin, and use a magic marker to put a mark on the face that lands up, without looking at the result. You then ask whoever feels like it to come forward, and show you their coin. I would still expect roughly the same number of heads and tails, but would you?
Edit: Spelling.
Fram kamerater!
This message last edited by Tor on 31/10/2012 at 09:34:49 AM
The Bell Curve revisited
29/10/2012 09:44:09 AM
- 1371 Views
Re: The Bell Curve revisited
29/10/2012 10:21:27 AM
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That's incorrect...
29/10/2012 10:26:49 AM
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Re: That's incorrect...
29/10/2012 10:36:32 AM
- 769 Views
Re: That's incorrect...
29/10/2012 10:40:27 AM
- 621 Views
Re: That's incorrect...
29/10/2012 10:42:57 AM
- 622 Views
Hehe...There are a few disputing it vocally. Whether they're in their right mind, well...
29/10/2012 10:45:07 AM
- 712 Views
Re: Hehe...There are a few disputing it vocally. Whether they're in their right mind, well...
29/10/2012 10:49:49 AM
- 606 Views
Re: Hehe...There are a few disputing it vocally. Whether they're in their right mind, well...
29/10/2012 10:56:37 AM
- 691 Views
It's only as skewed as it seems when you make the assumption that the Forsaken
31/10/2012 04:34:11 AM
- 901 Views
RJ the physicist didn't know math, so that Shannow could be right...
29/10/2012 02:11:19 PM
- 645 Views
Re: RJ the physicist didn't know math, so that Shannow could be right...
29/10/2012 02:37:33 PM
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there are dozens of reasons for this
29/10/2012 08:18:18 PM
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Re: there are dozens of reasons for this
29/10/2012 09:07:35 PM
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Again I don't argue that genetics play no role
30/10/2012 01:57:24 AM
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Once again just so,we are clear on my stance with Genetics and Strength
30/10/2012 03:27:11 PM
- 611 Views
That the 1000 Novices aren't a random sample of the population?
29/10/2012 08:23:47 PM
- 550 Views
And why would it be biased towards those with lower strength?
29/10/2012 09:11:25 PM
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Absolutely no reason...
30/10/2012 01:35:35 AM
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Re: Absolutely no reason...
30/10/2012 06:43:54 AM
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Only if it was a random sampling. Which this is not.
30/10/2012 01:58:34 PM
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That's exactly the point. I want you to explain why it wasn't random.
30/10/2012 02:14:59 PM
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It wasn't random because it was a self-selected sample!
30/10/2012 02:43:03 PM
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Re: It wasn't random because it was a self-selected sample!
30/10/2012 02:47:30 PM
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Go read a stats text will you?
30/10/2012 02:54:16 PM
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Done
31/10/2012 09:34:11 AM
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You seem to have perfected whining to a Talent...
10/11/2012 10:14:19 PM
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Re: You seem to have perfected whining to a Talent...
11/11/2012 11:37:16 AM
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Seriously? I went and looked at some statistics books, and you won't even reply?
01/11/2012 12:13:49 PM
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Yes that totally makes sense
30/10/2012 08:07:16 AM
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That's not what happened...
30/10/2012 02:01:52 PM
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I hate to get into these things
29/10/2012 05:45:50 PM
- 725 Views
I would love for you to be right, because it would solve all our problems, but 0 is the challenge...
29/10/2012 07:56:34 PM
- 653 Views
In the truest sense, you are probably right that it is skewed
29/10/2012 08:20:52 PM
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Overwhelm Lanfear, not match her. *NM*
29/10/2012 08:26:09 PM
- 355 Views
Truth is, Moiraine was being overly optimistic...
29/10/2012 08:39:17 PM
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You're pathetic...
30/10/2012 01:20:01 AM
- 567 Views
The quote isn't specific
30/10/2012 08:32:36 AM
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Yet neither of them are at full potential and at least equal a Forsaken
30/10/2012 03:45:24 PM
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Re: In the truest sense, you are probably right that it is skewed
29/10/2012 09:10:27 PM
- 599 Views
Lots of people mean perfectly normal distribution when they say it
30/10/2012 05:25:35 PM
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Couldn't the Towers method of obtaining Aes Sedai be to blame?
30/10/2012 12:04:01 AM
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Re: Couldn't the Towers method of obtaining Aes Sedai be to blame?
30/10/2012 09:33:44 AM
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Are you sure about that?
30/10/2012 12:03:43 PM
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Re: Are you sure about that?
30/10/2012 12:19:34 PM
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That doesn't seem a coherent narrative to me
30/10/2012 04:26:25 PM
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Sharina did not have the Spark, nor did Nicola
30/10/2012 05:16:40 PM
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Re: Sharina did not have the Spark, nor did Nicola
30/10/2012 05:54:41 PM
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We do not know if Cadsuane or any of the Forsaken are Sparkers
30/10/2012 10:33:55 PM
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Re: We do not know if Cadsuane or any of the Forsaken are Sparkers
31/10/2012 12:30:52 AM
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A handful of examples are all we have and we have proof that an extremely strong Channeler
31/10/2012 02:58:57 AM
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you're confusing 2 things
30/10/2012 04:27:32 AM
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One thing
30/10/2012 05:23:17 PM
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That's the problem. The BC RJ has "built" has a minimum and a maximum value
30/10/2012 05:48:55 PM
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