Bias Sampling

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A store manager wants to estimate the proportion of all the customers of the store who would use store credit card for their purchases. The manager selects a random sample of 1,000 customers from their customer loyalty program list and sends them a survey asking if they would be interested in applying for a store credit card. Seventy-eight customers respond to the survey. What kinds of biases are evident in this scenario? Select all that apply.

• Non-Response Bias

• Response Bias

• Undercoverage Bias

• Volundary Response Bias

A store manager wants to estimate the proportion of all the customers of the store who would use store credit card for their purchases. The manager selects a random sample of 1,000 customers from their customer loyalty program list and sends them a survey asking if they would be interested in applying for a store credit card. Of the 78 customers who responded to the survey, 70 of them expressed interest in applying for a store credit card. Should the manager be concerned about these results? If so, why? Select all that apply.

• The manager should not be concerned about these results.

• Yes, because he should have asked more customers.

• Yes. Due to the low response rate, those who responded might be the people who are most interested in a store credit card and overestimate the population proportion of all customers who would be interested in a store credit card.

• Yes. Since he only asked customers from the store loyalty program, those customers may be more interested in a store credit card than all customers.

Tanya wants to know the percent of people likely to attend the upcoming musical at school. She asks each person in the musical how many people they know who are coming to make a prediction. Why is this sample biased?

• Drama students are more likely to lie.

• Musicals are better attended than plays.

• The drama teacher was not asked.

• The sample is not random and not representative of the entire school population.

Answer explanation

The sample is not random and not representative of the entire school population, as it only includes people involved in the musical, leading to bias.

In a certain school, students can choose whether to eat in the school’s cafeteria. A reporter working for the school’s newspaper polled students on their reactions to changes in the menu at the cafeteria. For each student leaving the cafeteria in one 20-minute time period, the reporter used a die to determine whether to stop the student and ask how he or she felt about the new menu. In the reporter’s article it was stated that a random sample of the students showed that 23% of the school’s student population was happy with the new menu. Which of the following statements is true?

• Because each student leaving the cafeteria was randomly selected and could choose to answer or not, this is a random sample of the student population, and the 23% is an accurate measurement of the school population’s view of the new menu.

• Because students self-selected whether to eat in the cafeteria, the sampling method might be biased and the sample might not be representative of all students in the school.

• The survey would have been more effective if the reporter had collected the data in one 10-minute time period rather than in one 20-minute time period.

• The survey would have been more effective if students who cared about the food could have called the reporter to tell how they felt about the new menu, so that only students with opinions on the subject would have been surveyed.

• Because no treatment was imposed on the students eating in the cafeteria, one cannot make any conclusions about the new menu.

In order to estimate the proportion of students that text while driving, a school administrator selects a simple random sample of students from a list of all students at the school who have parking permits. The students are called to the office, one at a time. The administrator asks each student, “Do you text while driving, even though you are not supposed to?” Based on the survey, the administrator estimates that only 2% of students with parking passes text while driving. What potential bias is present in the design of this survey and what is the likely direction of the bias?

• The sample proportion is likely an underestimate of the population proportion due to response bias.

• The sample proportion is likely an underestimate of the population proportion due to undercoverage.

• The sample proportion is likely an underestimate of the population proportion due to nonresponse.

• The sample proportion is likely an overestimate of the population proportion due to response bias.

• The sample proportion is likely an overestimate of the population proportion due to undercoverage.

I want to estimate the proportion of all adults in Chula Vista who graduated from high school. I select a random sample of addresses and go to those houses. When an adult answers the door, I ask if they had graduated from high school. If a child answers the door, I ask for an adult. If there is none there at the time, I return at another time to complete the survey. What is the most prominent bias?

• Non-response bias

• Response bias

• Voluntary response bias

• Undercoverage

I want to estimate the proportion of all adults in San Mateo who graduated from high school. I select a random sample of addresses and go to those houses. When an adult answers the door, I ask if they had graduated from high school. If a child answers the door, I ask for an adult. If there is none there at the time, I return at another time to complete the survey. What is the most prominent bias?

• Non-response bias

• Response bias

• Voluntary response bias

• Undercoverage

Why do we randomly select our samples?

• for control

• reduce bias

• so we don't get the same answers from everyone

• to eliminate confounding results