Recent surveys suggest that over 70% of university students experience significant exam-related anxiety, prompting researchers to seek accessible interventions. One proposed solution is the use of brief, app-based mindfulness exercises. Researchers want to investigate the effectiveness of a new 10-minute daily mindfulness app. They plan to recruit participants by posting an advertisement on the online student portal of the Psychology Department at a single highly-selective university, asking volunteers to complete an online self-report questionnaire.
Identify one reason why this study might have low population validity.
