An automotive service center would like feedback on its customer service. Each customer receives a printed card after they pay for services with a short survey on which customer service is ranked on a scale from 1 (least
satisfied) to 5 (most satisfied). Customers can then choose to submit the card in a box on their way out of the store.
The store manager finds that 140 cards were filled out in the past week, with an average customer satisfaction
score of 2.47. Which type of bias is most likely to be present in the survey results?