Notes on correctness of p-values when analyzing experiments using SAS and R

Abstract

It is commonly believed that if a two-way analysis of variance (ANOVA) is carried out in R, then reported p-values are correct. This article shows that this is not always the case. Results can vary from non-significant to highly significant, depending on the choice of options. The user must know exactly which options result in correct p-values, and which options do not. Furthermore, it is commonly supposed that analyses in SAS and R of simple balanced experiments using mixed-effects models result in correct p-values. However, the simulation study of the current article indicates that frequency of Type I error deviates from the nominal value. The objective of this article is to compare SAS and R with respect to correctness of results when analyzing small experiments. It is concluded that modern functions and procedures for analysis of mixed-effects models are sometimes not as reliable as traditional ANOVA based on simple computations of sums of squares.

Published in

PLoS ONE
2023, Volume: 18, number: 11, article number: e0295066

SLU Authors

• Al-Sarraj, Razaw

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

• Forkman, Johannes

  • Department of Crop Production Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Probability Theory and Statistics


More information

Correction in: Plos One, Volume 18, Issue 12, Article Number e0296235, DOI: 10.1371/journal.pone.0296235


Publication identifier

DOI: https://doi.org/10.1371/journal.pone.0296235

Permanent link to this page (URI)

https://res.slu.se/id/publ/127471