sampling AP STATS

stratified random sample

- choose a SRS from each stratum -combine the (SRS) into one overall sample -ensures all sub-groups in the population are represented in the sample

cluster sampling

-take SRS of clusters -use every member of the selected clusters in the sample

respone bias

people respond to questions inaccurately

Randomly select one of the first 5 students to arrive to class, and every 5th student thereafter to take the survey

A college professor wants to survey a sample of students taking her large lecture course. There are about 150students in the course, and 10 of those students are graduate students. She wants to take a systematic random sample of approximately 30 students. Which of these strategies will accomplish her intended design? Choose 1 answer:

It will probably be easier to weigh heavy slabs that are stacked together rather than pulling out some slabs from different stacks. Each stack has a variety of slabs, so choosing all of the slabs in some of the stacks should represent the population fairly well.

A warehouse stores thousands of marble slabs of different shapes, sizes, and materials that are used for construction projects. The manager wants to estimate the average weight of these slabs. The slabs are arranged in stacks that have about 10 slabs of different varieties. The manager wants to weigh a random sample of 100 slabs. Why might the manager choose a cluster random sample instead of a stratified random sample in this setting?

The population is all seniors at Riverview High; the sample is the 100100100 seniors surveyed.

Administrators at Riverview High School surveyed a random sample of 100 of their seniors to see how seniors at the school felt about the lunch offering at the school's cafeteria. Identify the population and sample in this setting:

Amira will sample more than 10 pizzas if she uses k=10. Amira will sample more than 10 pizzas if she uses k=17.

At Amira's pizza shop, they open a fresh batch of pizza sauce for every 10th pizza they make. Amira decides she wants to take a sample of pizzas in a given day and evaluate their overall quality. Her shop makes approximately 150pizzas per day, and she doesn't want to sample more than 10 pizzas for time's sake. Amira decides to use a systematic random sample where she'll evaluate every kth pizza made that day. Why might Amira choose k=17 instead of k=10? Choose all answers that apply:

simple random sample

Each law firm in one state registers its phone number with the state court system. An employee of the state court system uses a computer to select 500 random registered phone numbers, and the law firms associated with those numbers will be selected for an audit. What type of sample is this?

All first-year students, but only those who live in these 12residence halls

First-year students at a certain large university are required to live on campus in 1 of the 24available residence halls. After their first year, students have the option to live away from campus, but many choose to continue living in the residence halls. Estella oversees 12 of these residence halls. Her department surveyed a large simple random sample of first-year students who live in those 12residence halls about their overall satisfaction with campus living. Estella can safely generalize the results of the survey to which population? Choose 1 answer:

simple random sampling (SRS)

N= sample size every group of n individuals has an equal chance to be selected as the sample

Systematic Random Sample

Security workers at an airport randomly choose one of the first 505 people to pass through a checkpoint for extra security screening. After that person, they choose every 50 the start superscript, start text, the end text, end superscript person who passes through for extra screening as well. What type of sample is this?

The population is the occupants of all seats in the sports stadium; the sample is the occupants of the 80selected seats.

The owners of a sports stadium wanted to predict what additional refreshment options would sell well. They selected 80seat numbers at random and surveyed the occupants of those seats. Identify the population and sample in this setting.

strata

groups of individuals in a population who share characteristics thought to be associated with the variables being measured in a study

vouluntary response sample

people choose themselves by responding -intrest polls -people w/strong opinons are more likely to respond than those with more netural opinons - negative opinons

Nonresponse

people selected for the study are unable or unwilling to respond ex- mail surveys

Undercovarage

some members of the population arent represented in the sample

bias

the design of a study is likely to overestimate or underestimate the value you want to know

Population

the entire group of individuals that we want information about

systematic random sampling

-make list of population -randomly choose one of the first individuals - choose every kth individual after that ex- choose person 10 -choose every 10th person after

People may not want to admit that they plan on staying home rather than voting, so this is likely an underestimate. (people who aren't planning on voting may not want to admit that, since voting is generally framed as a positive act. in contrast its less likely for someone to say they don't plan on voting when they actually are going to vote , so 5% is probably an underestimate of who will stay home)

A campaign manager is curious what percent of voters will and will not vote in an upcoming election. They carry out a phone poll on a random sample of registered voters that includes the question, "Will you stay home and pass up your opportunity to vote in the upcoming election?" Only 5%, percent of the 250 people reached in the poll say they plan on staying home. why will this be a over/under bias.

Only those viewers who called in

A news program invites its viewers to call in and share their position on a proposed tax increase. Ninety percent of the viewers that call in say that they will vote against the tax increase. For which population is 90%, percent a legitimate estimate of the percent of voters who will vote against the tax increase? Choose 1 answer:

The population is the parents of the pediatrician's patients; the sample is the 10 parents of patients selected.

A paediatrician randomly selected 10 parents of his patients. Then he surveyed the parents about their opinions of different kinds of diapers.

The poll excludes people too young to vote.

A polling firm wants to contact a random sample of people likely to vote in an upcoming nation-wide election. They will use a random digit dialer to generate and call phone numbers at random, so the poll will include people with landlines, unlisted numbers, and mobile phones. The random digit dialer skips invalid phone numbers. If a person doesn't answer a call, the dialer will try one more time, and then skip that number. When a person does answer, a pollster asks a set of initial questions—such as the person's age and whether or not they voted in previous elections—to see if they are likely to vote in the upcoming election. If they are eligible and likely to vote, the pollster will then ask a series of questions about the election. Which of the following is not a potential source of bias in their poll?

stratified random sample

A school chooses 333 randomly selected athletes from each of its sports teams to participate in a survey about athletics at the school. What type of sample is this?

Voluntary response sample

A store prints a request on each receipt asking customers to fill out a satisfaction survey online if they are willing. What type of sample is this?Voluntary response sample

voluntary response sample

A support hotline asks callers to stay on the line after they have completed their call to respond to a short survey. What type of sample is this? Choose 1 answer:

(bias from) 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?

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. What type of sample is this?

Only the top 200longest streaks worldwide in June

Kara, who lives in Canada, plays a popular online video game where every round has a winner. Her best streak is 21 wins in a row, and she wonders how that compares to other players. The game's website has a worldwide leaderboard of players with the longest win streaks for each month. Kara finds that the top 200longest streaks in the world in June had an average of about 63 wins in a row. For which population is 63 wins a legitimate estimate of the average longest streak? Choose 1 answer:Choose 1 answer:

Randomly select 444 issues, and examine every page in those issues.

Lilian's favorite magazine published 50 issues last year, and each issue contained approximately 250 pages. She wants to take a cluster random sample of about 1,000 total pages to estimate what proportion of all pages contained an advertisement. Which of these strategies will accomplish her intended design? Choose 1 answer:

Employees may not want to give critical feedback in person to their manager, so this is likely an overestimate of Valerie's performance.

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." Which of these is the best explanation for why this result is probably biased?

The dermatologists at that session only

Various types of doctors attended a large medical conference. Someone leading a session asked the 30doctors in attendance how many years of experience they each had. The 15 dermatologists at the session had an average of 8 years of experience. For which population is 8years a legitimate estimate of the average experience? Choose 1 answer:

cluster

a group of individuals in the population that are near each other

sample

a subset of individuals in the population from which we actually collect data goal: use sample data to make inferences about population

convience sampling

chooses the individuals easiest to reach

random sampling

use a chance process to select a sample -sample is representative of the population -eliminates voluntary response bias - minimize under coverage example: drawing write each students name on identical slip of paper -place slips in hat and mix well -select 5 slips without replacement -use 5 selected slips as students as the sample

census

we collect data from every individual in the population - difficult, time consuming, extensive if population is large.

Some people might feel pressured to say they floss daily even though they don't.

A dentist wants to conduct a survey via telephone to determine what percent of all adults in their city floss daily. Which of these is the best example of response bias?

Response bias

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% percent 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. Which of these is the most concerning potential source of bias in the principal's poll?

Convenience sample

A quality control worker at a factory selects the first 101010 items she sees as her sample for the day. What type of sample is this?

Anyone who has taken a yoga class at the gym in the past year, but not before that

A large gym with hundreds of members offers yoga classes. Members are free to take these classes at no charge, but not all members are interested, and some never take advantage of the yoga classes. Non-members can also take these classes, but they must pay a fee for each class. A manager at the gym is curious about overall satisfaction with these yoga classes, so they survey a large random sample of anyone who has taken a yoga class at the gym in the past year. They find that 78%, percent of those surveyed are "very satisfied" with the yoga classes. For which population is 78%, percent a legitimate estimate of the percent of people that are "very satisfied" with the yoga classes? Choose 1 answer:

All first-year students at Duke University only

A large random sample of first-year students at Duke University—a private university in North Carolina—was polled about their overall satisfaction with campus living. To which population can the results of the poll safely be generalized?

Only duo mode players who play on any platform

A popular online video game can be played on multiple platforms: video game consoles, personal computers, and mobile devices. The game offers 3gameplay modes: solo, duo, and squad. Lee and Avery regularly play matches as teammates in duo mode on a video game console. They are curious how their average scores per match compare to other players. They use the game's website to take a large random sample of duo mode players on any platform. The sample has a mean of 585 points per match. For which population is 585 points a legitimate estimate of the average points per match?

Current students are not included in the sample.

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. Which of the following is not a legitimate concern about their survey results being representative of all graduates?

The population is every possible point on the car; the sample is the 30 selected points.

A quality control engineer is curious about the thickness of paint on a car at her factory. She randomly selects 303030 points on the car and measures the paint thickness at each of those points. Identify the population and sample in this setting. Choose 1 answer:

- voluntary response -under coverage -non response - response bias - connivence sample -random sample

sources of bias