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Author Topic:   most scientific papers are wrong?
Belfry
Member (Idle past 5111 days)
Posts: 177
From: Ocala, FL
Joined: 11-05-2005


Message 91 of 113 (285868)
02-11-2006 5:54 PM
Reply to: Message 90 by crashfrog
02-11-2006 5:04 PM


Re: A quibble -- sorry
crashfrog writes:
Samples of populations, analyzed for certain traits. So long as we're able to conclude that the distribution of the sample has a 5% chance or better of being a random deviation from the "expected" distribution of the population, we conclude that it is.
Like, if we have a sample of people and we're looking at their height, and we find that there's a 5% chance or greater that the difference between the distribution in our sample and the distribution in the whole is due to nothing more than chance, then we conclude that the sample we have is truly random, and not the result of some kind of selection for heights.
Again, unless I'm way off base, here, we take anything over 5% confidence. Yeah, I was surprised, too.
No, you're way off base - it's just the opposite. We consider it significant if there's less than a 0.05 probability (assuming the experiment was designed with a p<0.05 significance level) that the null hypothesis was rejected when it was in fact true (Type I error). Confidence intervals of 95% or 99% are commonly used.
Edit: I totally misread your posts, please disregard the above. Upon re-reading, if I'm seeing it right this time, you're saying that they do the same thing I described; they consider the difference to be statistically insignificant if there is a probability of 0.05 or more that it is due to random chance. But that means that they're working with a 95% CI.
This message has been edited by Belfry, 02-11-2006 05:54 PM
This message has been edited by Belfry, 02-11-2006 06:50 PM

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 Message 90 by crashfrog, posted 02-11-2006 5:04 PM crashfrog has not replied

  
Belfry
Member (Idle past 5111 days)
Posts: 177
From: Ocala, FL
Joined: 11-05-2005


Message 92 of 113 (285884)
02-11-2006 6:37 PM
Reply to: Message 83 by Percy
02-09-2006 9:45 AM


Re: A quibble -- sorry
Percy writes:
I used to do this stuff a little a couple decades ago, and without digging out my old equations my vague recollection, give or take a few but this probably isn't too far off, is that a random sample size of around 1700 is sufficient to have a degree of assurance of 95%. Surprisingly, this sample size is not a function of the size of the full population from which the random set is selected. In other words, whether you're sampling a population of a million or a billion, around 1700 is all you need for 95% assurance if your sample is randomly selected.
This is essentially true with regard to the margin of error in survey data characterizing a large population (for example, poll results), which I suspect would apply to the question at hand (error rate of scientific study conclusions). However, Inkorrekt is correct in that with many studies, results can be significant with much smaller sample sizes.

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 Message 83 by Percy, posted 02-09-2006 9:45 AM Percy has not replied

  
Belfry
Member (Idle past 5111 days)
Posts: 177
From: Ocala, FL
Joined: 11-05-2005


Message 101 of 113 (285984)
02-12-2006 3:58 PM
Reply to: Message 100 by inkorrekt
02-12-2006 3:19 PM


Re: Reagan started our long slide down to mediocrity.
inkorrekt writes:
Both opposing concepts [evolution and Intelligent Design] cannot be true. Only one has to be True.
This is not only logically false, it actually runs contrary to Intelligent Design as it is conceptualized by Behe et al. "Critical thinking" is only useful if you are well-informed about the issue.

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 Message 100 by inkorrekt, posted 02-12-2006 3:19 PM inkorrekt has not replied

  
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