Wijesuriya, B.W.Thattil, R.O.2012-06-252012-06-251997Journal of the Rubber Research Institute of Sri Lanka 80pp.53-59https://dl.nsf.gov.lk/handle/1/8934Comparatively little has been published on experimental techniques and statistical methods in rubber.This paper is a review of available literature on the use of covariates in experiments falling into immature and mature stages of rubber.The main objective is to encourage researchers to collect appropriate pre-treatment records to adjust the post.treatment variables so as to obtain high precision of results.In this connection,the effectiveness of rubber yield,girth and panel variables as pre-treatment records during the mature stages;seed and budded stump weights as covariates during the immature stages are discussed.The use of double covariance and other possible approaches to minimize initial variability in fertilizer,pest and disease,weed and green house experiments are also discussed.AgricultureRubberStatistical methodsArticle