In this online collaborative activity, adapted from a face-to-face tutorial activity, students each provided data and suggestions about its interpretation, by contributing to a series of wiki pages. They undertook an assessment question based on interpretation and implications of their findings. The activity involved probing questions inviting students to add comments about the interpretation and long-term implications of their results. It enabled weaker and less confident students, who reported finding the topic challenging, to build on comments from others and add their own valuable contributions. Nine participating students were asked in telephone interviews about their perceptions of the activity, and their comments were categorised. Categories included the visual, practical/authentic and collaborative nature of the activity, feeling of responsibility to the group, and deeper understanding of the topic. The relative importance of the aspects of the activity represented by these categories for more and less able students was explored using an optional online questionnaire. The activity is being adapted for use in other contexts in which a complex question, posed on a wiki, enables students to build on each other's responses to gain a deeper understanding, and therefore helps weaker or less confident students to understand particularly challenging concepts.