Considerations When Sampling Answers

A business developer would like to purchase an abandoned corner lot in a small town and build a small convenience store with gasoline pumps on the site. Town leaders are concerned about potential traffic and noise impact to the adjacent neighborhood and send printed surveys to 500 homes in the affected area. Of the 123 surveys returned, 87% oppose the plan to develop the corner lot. How could the sampling design cause town leaders to overestimate or underestimate overall support of the development plan?

Some government leaders propose allowing oil companies to drill in currently protected lands that may be rich in oil reserves. Environmental researchers argue that drilling in such lands would be harmful to the surrounding ecosystem. To measure support for drilling in such lands, an oil company representative uses random-digit telephone dialing to contact adults in the region and measure opinion for increased drilling. One question in the survey asks, "Given that an increase in drilling could result in increased tax revenue and additional jobs to the region, would you support a proposal to allow drilling in lands currently protected from drilling?” What type of bias could be most likely affecting the survey results?

Many large cities use taxes on entertainment tickets to pay for improvements to public facilities, like stadiums, arenas, and concert venues. A city council proposal would increase the current ticket tax in order to raise funds for a new public concert hall. Council representatives plan to conduct a survey outside of a large concert in the summer and ask selected adults if they would support an increase in the ticket tax to pay for the new concert hall. Which type of bias will most likely affect the survey results?

A large retirement community provides many activities for its residents. The activity director is considering adding a trivia night on Tuesday evenings if there is enough interest from the residents. To measure interest in the trivia night, the activity director leaves a printed survey in residents’ mailboxes, on which the resident can express whether they are interested. Of the 68 surveys returned, 55 expressed interest. Which of these describes the type of bias in this survey and a likely direction of the bias in estimating overall community support for the trivia night?

A restaurant chain would like to measure the proportion of customers who are generally satisfied with the service provided by its staff. At the end of the meal, as the check is delivered to the table, the server asks those at the table to rate their satisfaction with the service provided as "Very Satisfied,” "Satisfied,” or "Not Satisfied.” During a one-week period, 147 customers were surveyed and 135 (93%) reported they were either Satisfied or Very Satisfied. What type of bias may be present in the survey results?

A team of community members hopes to use land in a current empty lot for a dog park. To determine if the community generally approves of the use of the lot for a dog park, volunteers survey shoppers leaving a pet store located near the lot. The results show that 83% of the 112 people surveyed approve of the dog park plan. How might the survey results be biased in estimating community support for a dog park?

Many large cities have considered or passed proposals that ban the use of plastic grocery bags in stores. A concerned student would like to measure if residents of her hometown would consider a similar ban on plastic bags. Standing in a busy shopping area, the student approaches adults and asks, "Items made of plastics are a dangerous, growing source of pollution to our world’s oceans and threaten many animal species. Given this, would you support a ban on plastic shopping bags in our city stores?” How might the results of this survey be biased in estimating the proportion of all town residents who would support a ban on plastic bags?

To ease congestion in a downtown area, city planners are considering a plan to widen a major thoroughfare from two driving lanes to three driving lanes. This plan would require closing a section of downtown streets as the work begins. In order to assess public support for the plan, city planners provided a phone number to residents that could be used to register opinion for or against the plan. In total, 267 calls were received, with only 24% supporting it. Which statement describes the most likely type of bias in this setting?

Many adults owe money from their college loans for years into their professional careers. A newspaper would like to estimate the proportion of all adults in the city who have debts from college loans. To collect data, a random sample of 300 young adults between the ages of 25 and 35 is asked, "Do you have more than $5,000 in current college debts?” 68% of those sampled reported that they do have more than $5,000 in college-related debts. How might this sample be biased in obtaining an estimate of all adults in the city who have college debts?

An executive for a large company is considering a change to health insurance plans offered to the employees. To assess employee satisfaction with the current plan, the executive sends an email to all company employees asking their opinion of the current plan. A summary of the results received shows that 27% of company employees are "highly satisfied” with the current health insurance plan. Which statement about the results is most likely to be true?

Residents of a community currently pay a fee for recreational services in their neighborhood, such as tennis courts, running trails, and a pool. To assess whether there is support for raising the fee for the upcoming summer, a random sample of 50 residents is contacted and asked this question: "Would you support a $10 increase in the recreational fee to support programs for the health and well-being of children in the community?” Of the 50 residents contacted, 42 approved of the fee increase. Which statement describes a likely source of bias present in the survey results?

A city government is considering raising the local income tax to pay for improvements to government facilities. A private citizen opposes the plan and stands on a busy street to survey residents with the question, "Do you agree that wasteful spending is a serious problem in our local government?” The results of the survey will most likely suffer from which type of bias?

A local baseball team is struggling this season, and many fans of the team believe it may be time to replace the head coach. To estimate support for firing the current head coach, a television news station provides a link on its website where fans of the team can respond to the question: "Do you feel the current head coach should be fired?” After 2,367 votes on the website, 79% of those who responded felt the coach should be fired. Which of these describes the type of bias in this survey and a likely direction of the bias in estimating overall support for firing the coach?

To estimate the proportion of city residents who shop online, a researcher visits a mall on a weekday morning and asks people she encounters to share their experiences with online shopping, including this question: "Do you shop online at least once each week?” The results show that 32% of shoppers shop online at least once per week. Which of these describes a likely source of bias present in the survey results?