Statistical Bias

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

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

Source of bias in which some groups of populations are LEFT OUT of the selection process

• Response Bias

• Undercoverage

• Convenience Sampling

• Voluntary Response

Organize these options into the right categories

Groups:

(a) Selection Bias

,

(b) Measurement Bias

,

(c) Nonresponse Bias

,

(d) Graphical Bias

• Only getting 20 responses out of the 200 people asked, but still making a claim about the data.

• Pi chart pieces are similar or the same colors.

• Only testing a medicine on middle-aged white men.

• The scale used in the study was not calibrated before testing.

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 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.

What are the potential consequences of bias in statistics?

• Misunderstood results, accurate conclusions, and fair treatment

• Accurate results, clear conclusions, and fair treatment

• No impact on results, accurate conclusions, and fair treatment

• Inaccurate results, misleading conclusions, and unfair treatment

How can bias in statistics be minimized?

• Using random sampling, ensuring a representative sample, and being transparent about the data collection process

• Using a small and unrepresentative sample

• Not being transparent about the data collection process

• Only using non-random sampling

The organizer of a 5K race wants to know how many miles per week runners typically run. To investigate, she surveys the first 30 people who check-in at her race. Which of the following statements is true?

• This is a voluntary response sample. It will likely overestimate the number of miles that runners typically run.

• This is a voluntary response sample. It will likely underestimate the number of miles that runners typically run.

• This is a convenience sample. It will likely overestimate the number of miles that runners typically run.

• This is a convenience sample. It will likely underestimate the number of miles that runners typically run.

The director of student life at a university wants to know what percent of students eat regularly on campus. To find out, the director selects a random sample of 300 students who live in the dorms. Is the percent from the sample likely an overestimate or underestimate of the percent for all students?

• Overestimate

• Underestimate

• Neither