An occupational psychologist was interested in the relationship between daily screen time and occupational burnout scores among corporate office workers. He conducted a correlational analysis to investigate this using a self-selected sample of 80 employees from a large multinational technology firm.
Each participant tracked their daily screen time for seven consecutive days using a background screen-monitoring app to calculate their average daily screen hours. Their occupational burnout level was then assessed using a standard online burnout inventory questionnaire.
Describe one weakness of using a self-selected sample in this study.