Stats Practice

Response Bias

A gas company takes a random water and soil sample nearby their plant to test for contamination and it comes back as "100% clean" what kind of sampling bias could this be?

Simple Random Sample

A manager associated each employee's name with a number on one ball in a container, then drew balls without looking to select a sample of 5 employees. What type of sample is this?

Some graduates won't check their emails and therefore won't respond (non-response bias) Graduates might claim they make more $ than they actually do (response bias)

A prestigious university wants to estimate the average starting salary of its graduates. The alumni outreach department sends an email to the most recent address they have on file for every graduate. The email asks the graduates to participate in a survey about their employment history and starting salary. What are some possible concerns?

sampling bias (undercoverage)

Before the 1936 US presidential election, a popular poll predicted that Alfred Landon would comfortably win against Franklin D. Roosevelt. The poll randomly sampled people from sources like telephone and car registration records, but the country was in an economic crisis, so many voters without those luxuries were not included in the poll. Voters with lower incomes favored Roosevelt, who ultimately won with 62% percent of the vote—one of the largest margins of victory ever in a US presidential election. Which type of bias does this scenario best describe?

People may feel pressured to say they floss more than they actually do in fear of judgement

If a dentist randomly asked people how often each individually flossed, what is the potential response bias?

Employees aren't going to want to give critical feedback on a manager, especially when its not anonymous

Valerie manages a team of 30 employees at a large company. She wants to survey members of her team on her performance as their manager. She holds an individual meeting with each of her team's members and asks them the same set of questions. Valerie finds that 83%, percent of her employees rate her performance as "outstanding." Why would this number not be accurate?

Cluster Sampling

What would this be an example of?

Continuous Variable

What would this be an example of?

Qualitative Data

What would this be an example of?

Simple Random Sample

What would this be an example of?

Stratified Random Sample

What would this be an example of?

Systematic Sample

What would this be an example of?

cluster sampling

A principal orders t-shirts and wants to check some of them to make sure they were printed properly. She randomly selects 2 of the 10 boxes of shirts and checks every shirt in those 2 boxes. What type of sample is this?

stratified random sample

A truck manufacturer selects 3 trucks at random from each of 6 models for safety testing. What type of sample is this?

quantitative data

What would this be an example of?

Discrete variable

What would this be an example of? (# of people)