A researcher sent out questionnaires to 5000 randomly chosen members of HMOs (health maintenance organizations). Only 1200 of these members completed their questionnaires and returned them. Seventy-eight percent of the respondents reported that they had experienced denial of claims by their HMOs. Of those who experienced such denials, 25% had been unable to resolve the problem to their satisfaction in at least one such instance. Write an article for a business magazine summarizing the results of the survey and cautioning the readers about possible bias in the results. Indicate which types of biases are likely to be present, how they could arise, and whether the percentages given above are likely to overestimate the true percentages of all HMO members who have experienced the denial of claims by HMOs.