Abstract:
This paper presents proper practice guidelines for simple and multiple linear
regression methods employing examples from the rubber sector. The main objective
of this study was to popularize analysis of residuals and diagnostic checking, which
are areas generally not given adequate thought while performing analysis and also
in reporting. The illustration 1 on simple linear regression was done to find out
whether the clones; RRIC100 and RRIC121 have a common relationship or have
different relationships between girth and yield. This paper suggested the way, the
model to be fitted and how the hypotheses to be tested for different slopes and
different intercepts. According to the analysis a common relationship exist between
girth and yield for the two clones which has an explanatory power of 69 %. The
illustration on multiple regression aimed to build the relationship between physical
factors of a smallholder rubber unit with the productivity. Tapping days and
tappable trees/ha were found to be the most decisive factors affecting productivity
of land. Problems encountered in residuals were successfully arrested by
transforming the dependent variable using logio value of productivity. The
explanatory power of the model was also improved to 26 % through this operation.
