497 – Advances in Nonparametric Testing: Part 2
The Median Test with Zero-inflated Distributions
William D. Johnson, PhD
Pennington Biomedical Research Center
Jeffrey H. Burton, PhD
Pennington Biomedical Research Center
Robbie A. Beyl, PhD
Pennington Biomedical Research Center
Jacob Romer
Pennington Biomedical Research Center
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.