Population vs. Sample
The entire group of individuals in a statistical study about which we want information.
What is the population?
A college student studying sleep habits hands out a questionnaire to their first 20 classmates in the 8:00 AM lecture.
What is convenience sampling?
The 3-word catchphrase used to remember how Stratified Random Sampling works.
What is "Some from ALL"?
A radio host asks listeners to call in and share their opinions on a statewide "bell-to-bell" restriction on cell phones in Illinois public schools.
What is voluntary response bias?
Six Flags wants to survey visitors. They get a master list of all season pass holders for the year, randomly choose 100 names, and call them. Identify the sampling frame.
What is the list of all season pass holders?
The part of the population from which we actually collect information.
What is a sample?
A radio host asks listeners to call a phone number to vote on a controversial news topic.
What is voluntary sampling?
What is "ALL for SOME"?
A political pollster calls landline telephone numbers to ask about voting intentions.
What is undercoverage?
Spotify sends a survey to 500 randomly chosen users. 320 users respond, but 20 of those submissions are left completely blank. Calculate the official sample size (n).
What is 300?
(320-20)
A teacher distributes 400 surveys, receives 250 back, but finds 30 of them are completely blank. _____ is the correct sample size.
What is 220?
250-30=220
A factory quality checker inspects every 20th bottle coming off an assembly line starting from a randomly chosen bottle.
What is systematic random sampling?
A car dealership splits its cars into Sedans, SUVs, and Trucks, then randomly selects 5 vehicles from each category to test.
What is stratified random sampling?
A survey is mailed to 100 randomly chosen households, but 70 of those households throw it in the trash without filling it out.
What is non-response bias?
A coffee shop chain wants to learn about customer habits. They group their stores by location type (Downtown, Suburban, Highway) and randomly select 20 customers from each location type. Identify the sampling method used.
What is stratified random sampling?
The list or collection of all individuals from which a sample could be selected, as opposed to those actually surveyed.
What is the sampling frame?
A concert organizer puts every ticket holder's name into a computer system, and the computer generates 20 winning names.
What is Simple Random Sampling (SRS)?
A youth soccer league with 30 teams wants to survey players about field conditions. The league director randomly selects 5 entire teams and surveys every single player on those 5 teams.
What is cluster sampling?
Asking students about their healthy eating habits right after watching a dramatic documentary about fast food is an example of this bias.
What is recency bias?
Addison's Lou Malnati's manager wants to learn about customer satisfaction. He posts a flyer on the front door asking customers to visit a website and fill out a feedback form for a chance to win $100. Identify the main type of bias created by this setup.
What is voluntary response bias?
Portillo's wants to know the satisfaction level of all its drive-thru customers. They randomly survey 500 drive-thru customers across 20 different store locations. Identify the population of interest.
What is all drive-thru customers of Portillo's?
A national polling organization randomly selects 10 states, then randomly selects 5 cities within each of those states, and finally randomly selects 20 households in each city to survey.
What is multi-stage sampling?
VASA Fitness wants to survey members about equipment preferences. They divide members into 3 age brackets (18–30, 31–50, and 51+) and randomly select 50 members from each age group to survey.
What is stratified random sampling?
A police officer walks into a classroom and asks students directly, "Have you ever broken the speed limit while driving?" This setup leads to this type of bias.
What is response bias?
A fitness influencer posts a survey about gym habits on their public Instagram story at 6 AM on a Monday and leaves it up for 2 hours. Name two distinct types of bias created by this setup.
What are voluntary response bias (people opt-in to participate) and undercoverage (excluding non-Instagram users, people sleeping at 6 AM, or non-followers)?