The hand- washing behavior of adults using public restrooms at airports was the subject of a study conducted by the American Society of Microbiology. A press release issued by the Society (September 15, 2003) included the following description: Although illnesses as deadly as SARS and as trouble-some as the common cold or gastric distress can be spread hand- to- hand, the survey sponsored by the American Society of Microbiology (ASM) found that many people passing through major U. S. airports don’t wash their hands after using the public facilities. More than 30 percent of people using restrooms in New York airports, 19 percent of those in Miami’s airport, and 27 percent of air travelers in Chicago aren’t stopping to wash their hands. The survey, conducted by Wirthlin Worldwide in August 2003, observed 7, 541 people in public washrooms in New York, Chicago, San Francisco, Dallas, Miami, and Toronto. These results were then generalized to people who use public restrooms. Answer the following four questions for this observational study.
a. What is the population of interest?
b. Was the sample selected in a reasonable way?
c. Is the sample likely to be representative of the population of interest?
d. Are there any obvious sources of bias?