Inference and Thick Tails: Some Surprising Results
Carlo V. Fiorio, University of Milan
Vassilis A. Hajivassiliou, London School of Economics
Download the Paper (PDF format) - May 3, 2007
Tell a colleague about it.
Printing Tips: Select 'print as image' in the Acrobat print dialog if you have trouble printing.
ABSTRACT:
This paper analyses the distribution of the classical t-ratio statistic from distributions with no finite moments and shows how classical testing is affected. Some surprising results are obtained in terms of bimodality vs. the usual unimodality of the standard studentized t-distribution prevailing in classical conditions. The paper develops a new distribution termed the “double Pareto,” which allows the thickness
of the tails and the existence of moments to be determined parametrically. We also consider infinite-moments distributions truncated on a compact support to investigate the relative importance of tail thickness in case of finite moments. We find that
the bimodality persists even in such cases.
Simulation results are used to highlight the dangers of relying on naive testing in the face of thick-tailed distributions. Special cases analyzed include one- and
two-sample statistical inference problems, as well as linear regression econometric problems.
SUBJECT AREA:
C14, C15, H2, I32
SUGGESTED CITATION:
Carlo V. Fiorio and Vassilis A. Hajivassiliou,
"Inference and Thick Tails: Some Surprising Results"
(May 2007).
UNIMI - Research Papers in Economics, Business, and Statistics.
Statistics and Mathematics.
Working Paper 24.
http://services.bepress.com/unimi/statistics/art24
Paper presented by C. Tommasi.
| 
