Stats online Ch. 10

Which matters more about a sample you draw from a​ population?

Choose the condition below that is more important when choosing a sample from a population. A. the size of the sample

Some friends of yours in a political science class are angry about a new town ordinance restricting​ off-campus parties. They make an online survey asking​ students' opinions. This type of sampling might be classified as a​ __________ sample.

Convenience

A company hoping to assess employee satisfaction surveys employees by assigning​ computer-generated random numbers to each employee on a list of all employees and then contacting all those whose assigned random number is divisible by 15. Is this a simple random​ sample?

D. Yes, this is a simple random sample. Each employee has an equal and independent chance of being selected.

An internet company conducts a global consumer survey to help multinational companies understand different consumer attitudes throughout the world. Within 30​ countries, the researchers interview 1000 people aged​ 13-65. Their samples are designed so that they get 500 males and 500 females in each country. Complete parts a and b below.

1. Are they using a simple random​ sample? Explain. B. No. It would be nearly impossible to get exactly 500 males and 500 females from every country by random chance. 2. What kind of design do you think they are​ using? B. A stratified​ sample, stratified by whether the respondent is male or female.

Administrators at a university were interested in estimating the percentage of students who are the first in their family to go to college. The university student body has about 57 comma 000 members. The university administration is considering a variety of ways to sample students for a survey. For each of these proposed survey​ designs, identify the problem.

1. Publish an advertisement inviting students to visit a website and answer questions. C. This would suffer from voluntary response bias. 2. Set up a table in the student union and ask students to stop and answer a survey. A. This would be a convenience sample.

Administrators at a university were interested in estimating the percentage of students who are the first in their family to go to college. The university student body has about 45 comma 000 members. For each scenarios a through​ c, identify the kind of samples used by the university administrators.

1. Select several dormitories at random and contact everyone living in the selected dorms. B. cluster sample 2. Using a​ computer-based list of registered​ students, contact 100 ​freshmen, 100 ​sophomores, 100 ​juniors, and 100 seniors selected at random from each class. A. stratified sample 3. Using a​ computer-based alphabetical list of registered​ students, select one of the first 30 names on the list at​ random, and then contact the student whose name is 60 names​ later, and then every 60th name after that. D. systematic sample

The company plans to have the head of human resources for each corporate division hold a meeting of their employees to ask whether they are happy on their jobs. They will ask people to speak out loud and indicate whether they are happy. What problems do you see with this​ plan?

A. The plan is likely to have biased results because employees​ won't want to express unhappiness in front of their supervisors or their coworkers.

The president of the university plans a speech to an alumni group. He plans to talk about the proportion of students who responded in the survey that they are the first in their family to attend​ college, but the first draft of his speech treats that proportion as the actual proportion of current students who are the first in their families to attend college. Explain to the president the difference between the proportion of respondents who are first attenders and the proportion of the entire student body that are first attenders. Use appropriate statistics terminology.

A. The proportion of students who responded in the survey that are the first in their family to attend college is a statistic. The proportion of all students that are the first in their family to attend college is a parameter. The statistic estimates the​ parameter, but is not likely to be exactly the same.

What problems do you see with asking the following question of​ students? "Are you the first member of your family to seek higher​ education?"

D. Several terms are poorly defined. The survey needs to specify the meaning of​ "family" for this purpose and the meaning of​ "higher education." The term​ "seek" is also poorly defined as it does not specify what qualifies as seeking more education.

For their class​ project, a group of Business students decide to survey the student body to assess opinions about a proposed new student coffee shop to judge how successful it might be. Their sample of 220 contained 55 ​first-year students, 55 ​sophomores, 55 ​juniors, and 55 seniors. Complete parts​ (a) and​ (b) below.

1. Do you think the group was using an​ SRS? Why? B. No; it would be nearly impossible to get exactly 55 from each class by random chance. 2. What kind of sampling design do you think they​ used? A. a stratified sample

At its​ website, a polling company publishes results of a new survey each day. Scroll down to the end of the published results and​ you'll find a statement that includes words as shown below. Results are based on telephone interviews with​ 1,008 national​ adults, aged 18 and​ older, conducted on April​ 2-5, 2007 ... In addition to sampling​ error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.

1. For this​ survey, identify the population of interest. C. everyone in the nation that is​ 18+ years old 2. The company performs its surveys by phoning numbers generated at random by a computer program. What is the sampling​ frame? B. everyone with a telephone 3. What​ problems, if​ any, would you be concerned about in matching the sampling frame with the​ population? B. Some people do not have telephones.

You recently began an internship at your local chapter of savethepigeons.com. Concerned about a city ballot initiative dealing with the​ environment, you conduct a telephone survey of local residents. What are some possible sources of bias in your​ results?

Select all the possible sources of bias below: undercoverage of the population, non-response bias & response bias

The managers of a large company wished to know the percentage of employees who feel​ "extremely satisfied" to work there. The company has roughly 25 comma 000 employees. The company is considering ways to survey their employees.

1. Identify the problem with the proposed design. Select all that apply. B. This design would suffer from voluntary response bias. D. This design would be a convenience sample. 2. Identify the problem with the proposed design. Select all that apply. D. This design would suffer from voluntary response bias.

An amusement park has opened a new roller coaster. It is so popular that people are waiting for up to 3 hours for a​ 2-minute ride. Concerned about how patrons​ (who paid a large amount to enter the park and ride on the​ rides) feel about​ this, they survey the first 15 people in line for the roller coaster. Complete parts a through d below.

1. What kind of sample is​ this? C. a convenience sample 2. What is the sampling​ frame? C. all the patrons willing to wait in line for the roller coaster 3. Is the sample likely to be representative of the population of​ interest? B. No​, the sample is not likely to be representative of everyone in the park. 4. What members of the population of interest are​ omitted? C. the patrons who are not willing to wait in line for the ride

An amusement park has opened a new roller coaster. It is so popular that people are waiting for up to 3 hours for a​ 2-minute ride. Concerned about how patrons​ (who paid a large amount to enter the park and ride on the​ rides) feel about​ this, they survey every 20 th female as they enter the park comma starting from a randomly selected female. Complete parts a through d below.

1. What kind of sample is​ this? D. a systematic sample 2. What is the sampling​ frame? C. All the female patrons of the park 3. Is the sample likely to be representative of the population of​ interest? C. No​, the sample is not likely to be representative of everyone in the park. 4. What members of the population of interest are​ omitted? D. male patrons

When you sample so that every combination of individuals in your population has an equal chance of being chosen you are taking a​ __________.

simple random sample

A local TV station conducted a​ "Pulse-Poll" about the upcoming mayoral election. Evening news viewers were invited to text in their​ votes, with the results being announced on the​ late-night news. Based on the​ texts, the station predicted that the current mayor would win the election with​ 52% of the vote. They were wrong and the mayor​ lost, getting only​ 46% of the vote. Do you think the​ station's faulty prediction is more likely to be a result of bias or sampling​ error? Explain.

A. The​ station's faulty prediction is a result of bias. Only people watching the news will​ respond, and their preference may differ from that of other voters. The sampling method may systematically produce samples that do not represent the population of interest.