This study investigated the possession of science process skills of measurement and observation as determinants of students’ achievement in Chemistry practical. The study employed a correlation design. Two research questions and two hypotheses guided the study. Both purposive and random sampling techniques were used to select 10 schools out of 26 schools from and two hundred Senior Secondary two (SSII) Chemistry Students as the sample for the study by balloting with replacement. The students were exposed to a practical exercise (titration) for 60 minutes per group of five students. Two instruments: Assessment Format for Chemistry Students (AFCS) and Chemistry Practical Achievement Test (CPAT) were used to collect data. The Assessment Format for Chemistry Students (AFCS) was used to assess the students on the spot during the practical exercise and a four (4) point rating scale which was trial tested on 6 Chemistry students outside the schools for the main study. Six Chemistry teachers assessed the skills of measurement observation of the six students’ simultaneously. Through Inter Rater Reliability based on Kendal’s Coefficient of Concordance, a reliability coefficient of 0.86 was obtained indicating that the instrument (AFCS) was reliable. The CPAT has reliability coefficient of 0.88 based on test-re-test using Pearson Product Moment Correlation approach. The Chemistry Practical Achievement Test (CPAT) was used to obtain achievement scores of students on practical exercise which took six months to complete. A lesson plan guided the teaching of the skill to be measured. The values from AFCS and the scores from CPAT were analyzed for Correlation Coefficient using Pearson Product Moment Correlation Statistic for the research questions while step-wise linear regression analysis at 0.05 level of significance was used to test the null hypotheses. The results showed that students’ possession of measurement and observation skills determined to a high extent their achievement in Chemistry practical. There was a significant relationships between measurement and observation skills and achievement of students in Chemistry practical. Recommendations included that Chemistry practical be constantly conducted in schools and teachers should adopt guided discovery approach in teaching the theory aspect of chemistry.
