University of Exeter Handbook (Physics) Questions/Comments Department (Physics)

Group-Work and Assessment


Group work is a desirable part of the undergraduate physics curriculum because, inter alia:

Group Composition

In order to achieve the fairest outcome for all students [1] mixed-ability groups are preferred. The higher-ability and/or harder-working students have their greater contribution recognised in their individual mark so that they are not penalised by being obliged to work with lower-ability students.

Group Size

Increasing group size is known to decrease individual motivation [2]. Students also normally lack the management skills to organise large groups and to cope with the increased incidence of 'social loafing' in them [2]. Groups of four to six students work best for undergraduate projects. Groups of eight have been found to experience significant problems, e.g. when agreeing decisions, tracking progress, allocating tasks, and coordinating multiple activities. Groups with even numbers of students are preferred because Physics programmes give student a lot of practice at tackling tasks in pairs.


Numerous studies [3] have shown that group work can improve student performance, engagement, marks and retention. To achieve its potential, however, the assessment mechanisms must reinforce appropriate student behaviour. The literature yields three common approaches to assessment:

Sharp's Method

Sharp [4] presented an algorithmic method with a statistical basis for deriving individual student marks for a piece of group work from a single 'tutor' mark and ratings which students make of each other's contributions. The method incorporates a mechanism for directly controlling the size of the adjustments made. The original spreadsheet discussed by Sharp performed the the calculations necessary to apply the method and inspired the version that we currently use, which is available from the link below [5].

Sharp made the following assumptions:

and we use the following procedure, based on his recommendations:

  1. The final individual marks must lie within ±10% of the tutor's mark.
  2. A significance level of 25% is set for the statistic A, representing the the strength of the evidence which must exist that there were differing contributions between different the students before any changes are made.
  3. Students ratings:
  4. The tutor mark and ratings from each group are analysed using the spreadsheet [6]. This yields values of final student marks and the statistic A. If there is no variance in the ratings then A is undefined and each student receives the tutor mark. Otherwise, the value of A is compared to a critical value corresponding to a user-specified significance level. The table below gives some example values for reference purposes. If the observed value is below the critical value, then the spreadsheet parameter φ is set equal to zero for that group and again each student receives the tutor mark. Otherwise the individual marks calculated are examined to verify that they lie within the preset limits decided in advance. If they do not, the value of φ applied for that group is reduced until the range of individual marks is satisfactory.

Further details, notes and examples are provided with the spreadsheet linked-to by reference 5.

Group size, NCritical value of A

Table 1. Critical values for A at the 25% significance level.


  1. Group assessment in Systems Analysis and Design: a comparison of the performance of streamed and mixed-ability groups.
    M. Lejk, M. Wyvill and S. Farrow. Assessment and Evaluation in Higher Education (1999) 24(1) pp 5-14.
    DOI: 10.1080/0260293990240101.
  2. Dispensability of member effort and group motivation losses: Free-rider effects.
    N. L. Kerr and S. E. Bruun. Journal of Personality and Social Psychology (1983) 44(1) pp 78-94.
  3. The assessment of group work: lessons from the literature.
    G. Gibbs, ASKe, Oxford Brookes University (2009) [Accessed October 2011.]
  4. Deriving Individual Student Marks from a Tutor's Assessment of Group Work.
    S. Sharp Assessment and Evaluation in Higher Education (2006) 31(6) pp 329-343.
    DOI: 10.1080/02602930500352956.
  5. Spreadsheets for Assessing a Group Project Using Sharp's Method (v6)
    C. D. H. Williams (2017).


We are grateful to Dr Stephen Sharp for permission to repackage and publish his Peer Assessment of Student Groups spreadsheet (2004) licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported (CC BY-NC 3.0) License.

University of Exeter Handbook (Physics) Questions/Comments Department (Physics)