Studies/bias Unit 3

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% of the vote—one of the largest margins of victory ever in a US presidential election.

Bias from undercoverage

An airline company wants to survey its customers one day, so they randomly select 5 flights that day and survey every passenger on those flights.

Cluster random sample

Inspectors for a hospital chain with multiple locations randomly select some of their locations for a cleanliness check of their operating rooms. The inspectors check every operating room in the hospitals that were chosen.

Cluster random sample

A politician asks his neighbors their opinions about a controversial issue.

Convenience sample

They call 5,000 randomly selected phone numbers from a database containing the phone number of every customer. If someone selected doesn't answer, they'll attempt calling back up to 2 more times before giving up on reaching that person. They reach 350 customers with this strategy, and 60% of those reached say they are at least "somewhat concerned" about their personal information being shared without their knowledge or consent.

Nonresponse bias

Each student at a school has a student identification number. Counselors have a computer generate 50 random identification numbers, and the students associated with those numbers are asked to take a survey.

Simple random sample

A school chooses 3 randomly selected athletes from each of its sports teams to participate in a survey about athletics at the school.

Stratified random sample

A truck manufacturer selects 3 trucks at random from each of 6 models for safety testing.

Stratified random sample

The library where Kara works is planning to add a maker space where members can share equipment and services to create crafts. Kara randomly selected members from their database, then contacted them to ask what kinds of equipment and services they would be most likely to use.

sample survey

A famous study examined the smoking habits of British doctors and whether or not the doctors developed various types of cancers. Participants responded to questionnaires about their smoking habits and health in 1951, 1957, 1966, and many more times all the way up to 2001.

prospective study

A group of researchers wants to know whether graduates from different teacher preparation programs are more likely to stay in the profession. They select a stratified random sample of this year's graduates from several programs. The resterm-4earchers will contact the graduates after 1, 5, and 10 years to see whether they are teaching in those years.

prospective study

A high school has a policy that students' phones must be kept away during class. A principal used the school roster to poll a random sample of 50 students, and only 10%said that they ever had their phone out during class. The next day, the principal observed classrooms and noticed that approximately 25% percent of students had their phone out at some point during class.

response bias

Grace took a random sample of car accident records from the past 5 years in her country, and she calculated what percent of accidents in the sample were caused by married people. She compared that result with the percentage of all drivers in the country that were married during that time period.

retrospective study

Annabella was curious about why people choose to skydive. She randomly selected 10 flights that were carrying skydivers and interviewed all of the skydivers on the flights about their motivations.

sample survey