It is the goal of measurement to minimize errors in test scores. The extent to which errors from likely sources as examiners, items on a test, examiners and test administration occasions affect measures in the Senior School Certificate Examinations conducted by National Examinations Council (NECO) especially in technical subjects is not known. Generalizability coefficient obtained through analysis of variance components helps to address this problem with result of Dependability Index. This study therefore estimated the Generalizability and dependability coefficients of 2015 SSCE objective test in Electrical Installations and Maintenance Works (EI&MW). The objectives of the study were to: (i) estimate the variance in the 2015 SSCE objective test in EI&MW due to persons; (ii) estimate the variance in the 2015 SSCE objective test in EI&MW due to items used in the test; (iii) estimate the variance in 2015 SSCE objective test in EI&MW due to the interaction of persons by items; (iv) obtain the Generalizbility coefficient in the 2015 SSCE objective test in EI&MW; and (v) determine the Dependability coefficient in the 2015 SSCE objective test in EI&MW.rnOne-Facet Fully Crossed Design was used to carry out the study. The population comprised all the Senior Secondary School Students in Nigeria. Senior Secondary School Three (SS3) students offering Electrical Installations and Maintenance Works participated in the study. Out of the 3,448 students offering Electrical Installations and Maintenance Works in Nigeria, samples of 1,198 were selected. Senior School Certificate Examinations 2015 objective test in EI&MW was adopted as the instrument. The data obtained were analysed using Variance Components (VARCOMP); relative error variance, absolute error variance, Generalizability and Dependabilty coefficients statistics.rnThe findings of this study were:rni. variance accounted for in 2015 SSCE Electrical Installations and Maintenance Works for persons (Ïƒ2p) = 0.02 equivalent to 8% of the total variance;rnii. variance accounted for in 2015 SSCE Electrical Installations and Maintenance Works items (Ïƒ2i) = 0.03 equivalent to 12% of the total variance;rniii. variance accounted for in 2015 SSCE Electrical Installations and Maintenance Works persons by items (Ïƒ2pi,e) = 0.20 equivalent to 80% of the total variance;rniv. Generalizability coefficient of 2015 SSCE Electrical Installations and Maintenance Works was 0.80 andrnv. dependability coefficient of 2015 SSCE Electrical Installations and Maintenance Works was 0.78rnThe study concluded that Generalizability and dependability coefficients of 2015 objective test in EI&MW were high or acceptable. This revealed that the quality and numbers of items used in EI&MW were of acceptable standard. The study therefore recommended that the quality of the items in Electrical Installations and Maintenance Works objective test should be maintained. Furthermore the Evaluators should endeavour to carry out similar studies in other areas of vocational tests so that inference can also be made.