From: Robin Hanson (hanson@econ.berkeley.edu)
Date: Tue Sep 01 1998 - 10:36:35 MDT
Curt Adams writes:
>>http://homenet.andrew.cmu.edu/progress/research.html
>>
>>I find it thoughtful, careful, and persuasive. Contrary
>>to speculation on this list, the study gives clear
>>indications of direction of causality. Furthermore,
>>the study fits with my experience.
>
>I can't find any good indications of direction of causality. Indeed, the
>path analysis in Figure 1 explicitly assumes that internet usage
>affects followup psychological status and not the other way around.
Huh? Isn't there an arrow from the the lower left social/psych box
straight to the internet use box?
>The claim for causality is that initial loneliness and depression
>weren't associated with later internet use. However, depression *was*,
>it just wasn't significant. A non-significant p value is not evidence
>for no association; you need to look at confidence intervals, which
>weren't provided.
Re-examining Table 3, I find reasons for caution. Their format is odd,
relative to economics standards, as they don't include standard errors.
And the coefficient values of soc/psych influence on internet use are
about the same size as internet use influence on soc/psych. So I'd want
them to verify that the scaling of the parameters implies that in fact
the estimated influence one way is much bigger than the other way. Given
that they do that, I'd be comfortable again with their results.
>>I'll share this excerpt from their discussion section: ...
>This is a plausibility argument, not evidence.
Of course.
Robin Hanson
hanson@econ.berkeley.edu http://hanson.berkeley.edu/
RWJF Health Policy Scholar, Sch. of Public Health 510-643-1884
140 Warren Hall, UC Berkeley, CA 94720-7360 FAX: 510-643-8614
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