I'm not sure how many on this list follow David Levinson's blog The
Transportist (over here:
https://transportist.org/ ), but he recently
published a post about a working paper he co-authored with Alireza Emragun
titled "Transit Makes you Short": On Health Impact Assessment of
Transportation and the Built Environment.
The blog post is here:
https://transportist.org/2016/11/28/u-study-says-transit-does-not-have-impa…
The full paper is here:
http://conservancy.umn.edu/handle/11299/179812
Abstract:
The current research provides a test framework to understand whether and to
what extent increasing public transit use and accessibility by transit
affect health. To this end, the effect of transit mode share and
accessibility by transit on general health, body mass index, and height are
investigated, while controlling for socioeconomic, demographic, and
physical activity factors. The coefficient-p-value-sample-size chart is
created and effect size analysis are conducted to explore whether the
transit use is practically significant. Building on the results of the
analysis, we found that the transit mode share and accessibility by transit
are not practically significant, and the power of large-sample
misrepresents the effect of transit on public health. The results, also,
highlight the importance of data and variable selection by portraying a
significant correlation between transit use and height in a multivariate
regression analysis. What becomes clear from this study is that in spite of
the mushrooming interdisciplinary studies in the nexus of transportation
and health arena, researchers often propose short- and long-term policies
blindly, while failing to report the inherent explanatory power of
variables. We show that there is a thin line between false positive and
true negative results. From the weakness of p-values perspective, further,
we strove to alert both researchers and practitioners to the dangerous
pitfall deriving from the power of large- samples. Building the results on
just significance and sign of the parameter of interest is worthless,
unless the magnitude of effect size is carefully quantified post analysis.
~~~~~~~~~~~~
Ann Hartell
Doctoral Candidate
Institute for Multi-Level Governance and Development
Wirtschaftsuniversität Wien/Vienna University of Economics and Business
https://www.wu.ac.at/en/mlgd/ <http://www.wu.ac.at/mlgd/en/>
Personal:
annhartell.com
Email: ahartell(a)gmail.com