Analysis of covariance for completely randomized design (case study: the life times of cutting tools used with lathes

Abstract Analysis of covariance (ancova) is a blend of regression and analysis of variance (anova) used for upgrade precision of an experiment. Ancova can be used for all experimental design including completely randomized design. The completely randomized design is the response are randomly intrusted to treatments. Application ancova on completely randomized design in the manufacture is given to observe the effect of types of cutting tools of lifetimes of cutting tools . In this experiment covariate variable is lathe speed. Lathe speed affects tool life meaning that the involvement of the covariate variables in the covariance analysis model is appropriate. From the covariance analysis, it is also found that tool type influences tool life. The coefficient of variance in ancova is lower than anova. This proves that the ancova has a better level of precision than anova, so that ancova is more appropriate to use than anova.