On Thu, Feb 17, 2005 at 06:27:52PM +1000, Anthony Towns wrote:
> Joel Aelwyn wrote:
> >On Thu, Feb 17, 2005 at 11:53:47AM +1000, Anthony Towns wrote:
> >>martin f krafft wrote:
> >>>Maybe we should tabulate most commonly bashed roles and see if there
> >>>is a correlation with inavailability of information?
> >>What would be the point? That would tell us nothing about causation,
> >>which is the question at issue.
> >The assertion that causation and correlation are never tied is false.
>
> Good grief.
>
> Correlation tells you nothing about causation. It tells you that two
> things often occur together, so that when you find one, you'll often
> find the other.
Yes, it does. And with sufficiently high correlation, there is a high
probability that there is *some* sort of causative reason, whether it's
between the two or from a third source.
> >Or, in more homily terms:
> >If there's smoke, there may not be fire, but you'd still be well advised
> >to grab a fire extinguisher and check it out just in case.
>
> In particular, a correlation does not tell you which of the two events
> was the cause -- or even that there isn't a third event that was the
> cause. In Brisbane, high electricity use and high ice cream sales are
> correlated, but the underlying cause is hot weather, so manipulating
> either one won't assist with the other.
Quite. Of course, there's at least one more alternative: that the two
events are *both* causative to the other, leading to a feedback loop.
For example, "ftpmaster is effectively opaque" -> "people complain" ->
"ftpmaster becomes even less communicative". Just for an example.
> In the smoke versus fire case, you need to be careful that in looking at
> the correlation instead of the causation, you don't find yourself
> recommending people install exhaust fans instead of fire extinguishers.
True. However, if the smoke is persistant, you need to do *something* about
it, unless you enjoy choking on smoke. If you can't see the fire for the
smoke, and thus cannot establish whether there really is one at all, it
might be worthwhile to bring in a large fan and blow away some of the worst
smoke so you can tell what the heck is going on underneath and fix it.
--
Joel Aelwyn <fenton@debian.org> ,''`.
: :' :
`. `'
`-
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