Statisticians of medical colleges are involved in data analysis and interpretation of the results part of the manuscripts. The result part is the core of any research article but most of the main authors are not giving authorship to the statisticians and sometimes they just give an acknowledgement which is useless. Statisticians are not paid for their personal work. According to rules statisticians have to check and give the suggestions, not to analyse every article for free but still all will come from their analysis. Is it good practice?
I am adding the rule of International Committee of Medical Journal Editors below:
Authorship credit should be based on 1) substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; 2) drafting the article or revising it critically for important intellectual content; and 3) final approval of the version to be published. Authors should meet conditions 1, 2, and 3.