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Chapter 1: Problem 24

1.24 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 troublesome 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. (Hint: Reviewing Examples 1.3 and 1.4 might be helpful.) 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?

Short Answer

Expert verified
a. The population of interest is all adults using public restrooms at airports. b. The sample was selected reasonably but not perfectly as it was taken from only six airports. c. The sample might not be perfectly representative of the entire population due to different local characteristics and cultural differences. d. The geographic bias is an obvious source of bias as the study was conducted only in six specific airports.

Step by step solution

01

Define the Population

The population of interest in an observational study refers to the entire group that we want to draw conclusions about. In this case, the population of interest is all adults using public restrooms at airports.
02

Examine the Sample Selection

The sample selection refers to the group from the population that is actually studied. Here, the sample selection is people observed in public washrooms in New York, Chicago, San Francisco, Dallas, Miami, and Toronto. It is reasonable if it fairly represents the population.
03

Assess Representativeness of Sample

In order to be considered representative, a sample must accurately reflect the characteristics of the population of interest. This sample might be considered as reasonable but it might not fully represent all airport restrooms users, for various reasons such as time of observation, cultural differences and specific local characteristics.
04

Identify Possible Biases

Bias can occur if certain kinds of people are more likely to be included in the sample than others. Here, since only people from selected airports were observed, there is a geographic bias in the sample. The results may not apply to people using restrooms at smaller airports or in different geographical areas.

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