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A statistics professor wanted to find out the average GPA (grade point average) for all students at her university. She used all students enrolled in her statistics class as a sample and collected information on their GPAs to find the average GPA. a. Is this sample a random or a nonrandom sample? Explain. b. What kind of sample is it? In other words, is it a simple random sample, a systematic sample, a stratified sample, a cluster sample, a convenience sample, a judgment sample, or a quota sample? Explain. c. What kind of systematic error, if any, will be made with this kind of sample? Explain.

A statistics professor wanted to find the average GPA (grade point average) of all students at her university. The professor obtains a list of all students enrolled at the university from the registrar's office and then selects 150 students at random from this list using a statistical software package such as Minitab. a. Is this sample a random or a nonrandom sample? Explain. b. What kind of sample is it? In other words, is it a simple random sample, a systematic sample, a stratified sample, a cluster sample, a convenience sample, a judgment sample, or a quota sample? Explain. c. Do you think any systematic error will be made in this case? Explain.

A statistics professor wanted to select 20 students from his class of 300 students to collect detailed information on the profiles of his students. The professor enters the names of all students enrolled in his class on a computer. He then selects a sample of 20 students at random using a statistical software package such as Minitab. a. Is this sample a random or a nonrandom sample? Explain. b. What kind of sample is it? In other words, is it a simple random sample, a systematic sample, a stratified sample, a cluster sample, a convenience sample, a judgment sample, or a quota sample? Explain. c. Do you think any systematic error will be made in this case? Explain.

A company has 1000 employees, of whom \(58 \%\) are men and \(42 \%\) are women. The research department at the company wanted to conduct a quick survey by selecting a sample of 50 employees and asking them about their opinions on an issue. They divided the population of employees into two groups, men and women, and then selected 29 men and 21 women from these respective groups. The interviewers were free to choose any 29 men and 21 women they wanted. What kind of sample is it? Explain.

A magazine published a questionnaire for its readers to fill out and mail to the magazine's office. In the questionnaire, cell phone owners were asked how much they would have to be paid to do without their cell phones for one month. The magazine received responses from 5439 cell phone owners. a. What type of sample is this? Explain. b. To what kind(s) of systematic error, if any, would this survey be subject?

A survey based on a random sample taken from one borough of New York City showed that \(65 \%\) of the people living there would prefer to live somewhere other than New York City if they had the opportunity to do so. Based on this result, can the researcher say that \(65 \%\) of people living in New York City would prefer to live somewhere else if they had the opportunity to do so? Explain.

Explain the difference between an observational study and an experiment.

A federal govemment think tank wanted to investigate whether a job training program helps the families who are on welfare to get off the welfare program. The researchers at this agency selected 5000 : volunteer families who were on welfare and offered the adults in those families free job training. The researchers selected another group of 5000 volunteer families who were on welfare and did not offer them such job training. After 3 years the two groups were compared in regard to the percentage of families who got off welfare. Is this an observational study or a designed experiment? Explain.

Indicate whether each of the following constitutes data collected from a population or a sample. a. A group of 25 patients selected to test a new drug b. Total items produced on a machine for each year from 2001 to 2015 c. Yearly expenditures on clothes for 50 persons d. Number of houses sold by each of the 10 employees of a real estate agency during 2015

The number of shoe pairs owned by six women is \(8,14,3,7,10\), and 5 , respectively. Let \(x\) denote the number of shoe pairs owned by a woman. Find: a. \(\sum x\) b. \(\left(\sum x\right)^{2}\) c. \(\sum x^{2}\)