To Wash or Not to Wash
In a phone survey conducted by researchers for the American Society for Microbiology, 95% of the 1021 adults claimed they always washed their hands after using a public restroom.
Yet, when the researchers actually checked the veracity of this claim (by loitering in public bathrooms in five cites--Chicago, San Francisco, Atlanta, New Orleans, and New York), they observed that only 67% of the adults actually washed their hands.
Question: Can you explian why these two data values differ, when they apparently are measures of the same thing? Which data value do you think is correct, and why? How would you design a study that would produce (or verify) the correct data value?