Sampling
A principal groups students by homeroom and randomly selects 5 homerooms to survey all students about homework load. Which assumption must be reasonable for this sample to represent the school well?
Students within homerooms are heterogeneous (different)
A national fitness company wants to estimate the average number of gym visits per month among adults in the United States. Researchers stand outside several of the company’s most popular gym locations in major cities and ask entering members how many times they visit the gym each month. Based on the results, the company reports that the average adult visits the gym 11 times per month.
Undercoverage
A fitness app surveys only its paying subscribers to estimate average weekly exercise among adults. Explain why results cannot be generalized to all adults.
Selection bias/undercoverage
What are the prime factors of 24?
2 and 3
What is the world’s most populated city?
Tokyo, Japan
Which sampling method guarantees representation from important subgroups?
Stratified random sampling
Why is replication in experiments important?
It reduces variability
What book holds the record for the fastest selling book in history?
Harry Potter and the Deathly Hallows
A city recreation department wants to estimate the proportion of residents who plan to use a new community fitness center when it opens. The city has 8,000 adult residents and plans to survey 200 people. Which of the following sampling methods would result in a stratified random sample?
(A) Assign each resident a number from 1 to 8,000 and use a random number generator to select 200 residents.
(B) Survey the first 200 residents who sign up online to receive fitness center updates.
(C) Randomly select 200 residents from a list of people who already have gym memberships.
(D) Divide residents into two age groups (18–39 and 40+). Then randomly select 100 residents from each age group to survey.
D
A district surveys parents by emailing a questionnaire to families listed in the school newsletter database. Identify TWO potential sources of bias and explain briefly.
Undercoverage
Nonresponse
Ronald loves to can everything and is always working hard to improve his recipes. In 2023, he canned salsa. He was curious about what the level of salt content would have on the level of tastiness in his salsa, so in each of the five cans, he put different amounts of canning salt. In 2026, he opened those five cans and, through a double-blind taste test, rated each of them on a scale of 1 to 10, to see what level of salt maintained the best flavor level in his salsa. Identify the treatment, the experimental units, and the response.
Treatment: Salt
Units: Salsa Cans
Response: Rating Scale
What country hosted the 2022 World Cup?
Qatar