BIAS IN SAMPLES/SURVEYS STATS HONORS STUDY SET

Which direction of bias is more likely in this scenario 2?

The results are probably an overestimate of the percentage of all listeners that love the show.

Which direction of bias is more likely in this scenario 5?

The results probably underestimate of the percentage of students who smoke cigarettes.

Response bias

When something in the survey design influences the response. Someone could feel uncomfortable or reluctant to tell the truth. For example... Response Bias When something in the survey design influences the response. Someone could feel uncomfortable or reluctant to tell the truth. A man goes door-to-door to take a survey about support for the Boy Scouts. He is wearing his Boy Scout uniform.

Voluntary response sampling

When volunteering to respond, it is typical that only those who are passionate will respond to the survey or express opinions. This leads to lack of representation. For example... A radio host asks viewers to call in and answer a survey about their station. Everyone says they "love" his show.

Undercoverage bias

A portion of the population has been excluded from the sample or is not proportionally represented to how it is in the population. For example... A surveyor wanted to poll voters for an upcoming election and used a phone book to contact residents in his area.

Voluntary response sampling

Scenario 1: David hosts a podcast and he is curious how much his listeners like his show. He decides to start with an online poll. He asks his listeners to visit his website and participate in the poll. The poll shows that 89% of the 200 respondents "love" his show. What is the most concerning source of bias in this scenario?

Non response bias

Occurs when some individuals who are a part of the survey do not respond. Those who choose not to respond may differ from those who do. For example... A survey asks about cheating on standardized tests. Everyone who responded said they have never cheated on a standardized test.

Convenience sampling

Scenario 2: David hosts a podcast and he is curious how much his listeners like his show. He decides to poll the next 100 listeners who send him fan emails. They don't all respond, but 94 of the 97 listeners who responded said they "loved" his show. What is the most concerning source of bias in this scenario?

Undercoverage bias

Scenario 3: A senator wanted to know about how people in her state felt about internet privacy issues. She conducted a poll by calling 100 people whose names were randomly sampled from the phone book (note that mobile phones and unlisted numbers aren't in phone books). The senator's office called those numbers until they got a response from all 100 people chosen. What is the most concerning source of bias in this scenario?

Non response bias

Scenario 4: A senator wanted to know about how people in her state felt about internet privacy issues. She conducted a poll by calling people using random digit dialing, where computers randomly generate phone numbers so unlisted and mobile numbers can still be reached. They called over 1,000 random phone numbers—most people didn't answer—until they had reached 100 respondents. The poll showed that 46% of respondents were "very concerned" about internet privacy. What is the most concerning source of bias in this scenario?

Response bias

Scenario 5: A high school wanted to know what percent of its students smoke cigarettes. During the week when students visited the counselors to schedule classes, they asked every student in person if they smoked cigarettes or not. The data showed that 5% of students smoked cigarettes.

Biased wording

Scenario 6: A high school wanted to know what percent of its students smoke cigarettes. Counselors selected a random sample of students to take a survey on drug use. One of the questions reads, "If you are under the age of 18 years, do you illegally smoke cigarettes?" The data showed that 5% of students smoked cigarettes. What is the most concerning source of bias in this scenario?

Which direction of bias is more likely in this scenario 6?

The results probably underestimate of the percentage of students who smoke cigarettes.

Wording bias

Occurs if poor wording of a question results in lack of clarity ot if the question presents only one side of the argument (leading question). For example... A survey about foreign policy asks British citizens "How dumb is Rishi Sunak when it comes to foreign policy?"

Simple random sample (SRS)

In a simple random sample (SRS), every group is equally likely to be chosen.

Which direction of bias is more likely in this scenario 3?

42% is probably an underestimate of the percentage of people in her state concerned about internet privacy.

Which direction of bias is more likely in this scenario 4?

46% is probably an underestimate of the percentage of people in her state concerned about internet privacy.

Which direction of bias is more likely in this scenario 1?

89% is probably an overestimate of the percentage of all listeners that love the show.

Cluster sample

A cluster sample splits a population randomly into groups based on location (clusters). Then, sample everyone in the cluster.

Convenience sample

A convenience sample samples individuals who are easy to reach.

Stratified sample

A stratified sample splits a population into groups (strata) and chooses an SRS from each group.

Voluntary sample

A voluntary sample allows people to choose to participate in the sample.