Stats 3 Day 5 Chapter 12

Do Now Designing a Political Survey

Sampling vs Census Almost impossible to gather information from an entire population, so we take a sample Census: gathering data from the entire population Sample: small group of individuals selected to represent the population Sample survey: polling (asking questions of) a small group of people to learn about the population

Steps to make Sample Survey 1. Define the population you want to describe 2. Say what you want to measure about the population 3. Decide how to choose a representative sample (avoid bias)

How can a sample misrepresent a population? Bias 1. Voluntary response bias 2. Convenience bias 3. Undercoverage 4. Nonresponse bias 5. Response bias

Voluntary Bias A large group of people (or the whole population) are invited to respond, and those who do respond are counted in the survey People who volunteer to respond feel strongly about the topic Only those who volunteer become the sample

Convenience Bias Survey the people who are convenient to reach or by using a convenient method (like the internet)

Undercoverage Some portion of the population is not sampled at all or has a smaller representation than it has in the population

Nonresponse Bias When people are unwilling or incapable of responding. Those who don’t respond to the survey change the survey results Voluntary vs Nonresponse: Volunteers are the sample (voluntary) Everyone is the sample, but only hear from the volunteers (nonresponse)

Response Bias Anything in the survey design that influences the responses The wording of the questions may target certain people or sway the respondent in a certain direction Many respondents want to respond with what they think they “should” put

Bias in the News

Determine the Bias Worksheet

Activity Part 1 Design a survey about Pritzker (any topic you would like with improvement in mind) Example Topic: designing a survey that determines people’s satisfaction with RCPU

Activity Part 2 If the sample chosen was this class, examine your survey for bias: 1) determine the type of bias 2) strategize on a way to avoid or eliminate the bias from your survey

How to avoid bias… 1. Randomize 2. Sample Size

Homework