This report describes a small study that analysed module marks of one cohort of science undergraduates from one academic year. It explored how group summative assessment marking affected the overall marks in comparison with individual assessment. A tutor allocated students to mixed ability project groups. Individual marks for the group work component were derived by tutor-, peer-, and self-assessment weighting. The results showed that students with high individual marks obtained lower marks in the group component. Similarly, students with low individual marks obtained higher marks in the group component. Study limitations, results and conclusions are reported. (Contains 2 figures and 1 table.)