The Median Test with Zero-inflated Distributions

• Activity Number: 497
• Type: Contributed
• Date/Time: Wednesday, August 12, 2015 : 8:30 AM to 10:20 AM
• Sponsor: Section on Nonparametric Statistics
• Author(s): William Johnson* and Robbie A. Beyl and Jeffrey Burton and Jacob Romer
• Companies: Pennington Biomedical Research Center and Pennington Biomedical Research Center and Pennington Biomedical Research Center and Pennington Biomedical Research Center
• Keywords: Asymptotic chi-square test ; Zero-inflated distributions ; Large sample test ; Median test ; Nonparametric test

Abstract

The median test is often used to compare two or more distributions that have similar but asymmetric shapes and is typically used as an alternative, nonparametric approach to other tests of location such as the t-test. In the case of zero-inflated distributions, it is of interest to compare the distributions with respect to their proportions of observed zero values coupled with the comparison of the medians for their observed non-zero values. We present an application of the median test to simultaneously test the equality of the proportions of zeros as well as the medians among several groups. Results of simulation studies are reported to summarize some characteristics of the test.