The involvement of older people in research on digital technologies is uneven. Some groups of older people, e.g. the older ones, are less likely to participate in research which evaluates new digital technologies, compared to their counterparts. This may bias research results and produce wrong research conclusions. In this work, we aim at understanding whether and how the uneven involvement of older people in research on digital technologies has an impact on the research results. Our example is an intervention study which evaluated a web-based system for monitoring the postoperative progress of individuals after day surgery, i.e. ‘Mobile Phone in Recovery after Ambulatory Surgery’ (MIRAS). We considered a sample of 717 individuals of age 50 years and older (mean age: 65) who underwent a day surgery at one of the MIRAS recruitment sites during the recruitment timeframe. This group included both MIRAS participants and those who were not recruited byMIRAS. Based on information on age, gender, recruitment status, and intervention results, we implemented a weighting procedure to adjust the intervention results for the over-representation and the under-representation of groups of older people in the MIRAS sample by age and gender. We found that weighted and unweighted intervention results differed one another. The unweighted intervention results were over-positive with regards to the efficacy of the intervention due to the under-representation of groups of older people who were older and men. Biased results generate inaccurate conclusions which, in turn, can inform inappropriate digitalisation strategies and policies.