1. Intro to Stats and Collecting Data

"Determine whether the data set is a population or a sample. Explain your reasoning.

A survey of 250 members from an organized union of over 20,000 members"

The Challenge in Polling One of the challenges in polling for elections is deciding who to include in your frame and who might actually turn out to vote.

Suppose you were asked to conduct a poll for a senatorial election. Explain how you might design your sample. In your explanation include a discussion of the difference between “registered voters” and “likely voters.” What role would stratification play in your sampling?

A regional store manager wants to test whether increasing store hours increases profits, so they randomly select half of their locations to stay open an extra hour later in the evenings and compare profits between stores at the end of the month. They notice that stores open later saw higher profits on average. Is this an experiment or an observational study? Can they determine the extra hours caused the increase in sales? 

Sleepy Again Suppose you want to study the number of hours of sleep full-time college students at your college get each evening. To do so, you obtain a list of full-time students at your college, obtain a simple random sample of ten students, and ask each of them to disclose how many hours of sleep they obtained the most recent Monday.

a. What is the population of interest in this study? What is the sample

A company wants to test the effectiveness of a new acne cream. The company recruits 500 girls ages 13 to 17 who have acne. The subjects are randomly assigned into two groups. One group is given the acne cream and the other is given a placebo that looks exactly like the acne cream. Both groups apply the cream daily for two months. Facial photos are taken at the beginning and end of the treatment to compare results.

b. Identify a potential problem with the experimental design being used and suggest a way to improve it.

A company wants to test the effectiveness of a new acne cream. The company recruits 500 girls ages 13 to 17 who have acne. The subjects are randomly assigned into two groups. One group is given the acne cream and the other is given a placebo that looks exactly like the acne cream. Both groups apply the cream daily for two months. Facial photos are taken at the beginning and end of the treatment to compare results.

Identify the experimental units and treatments used in this experiment.

Identify the population and the sample. Describe the sample data set.

A survey of 214 of the seniors graduating with a bachelor of science degree from a university found that 15% planned to obtain entry-level jobs in the health field.

"Determine whether the data set is a population or a sample. Explain your reasoning.

The salary of each employee of an advertising firm"

In Exercises 29–32, indicate whether the observational study used is cross-sectional, retrospective, or prospective.

Heart Health Study Samples of subjects with and without heart disease were selected, and then researchers looked back in time to determine whether they took aspirin on a regular basis.

Robocalls According to Martin Boon of ICM Limited, a polling firm in Britain, in 1995 it took 3000 to 4000 phone calls to obtain a sample of size 2000. Today, it takes over 30,000 calls. To reduce costs, more polling is done using robocalls and Internet-based polling. Robocalling to cellular telephones is illegal. How do these methods potentially lead to nonsampling error? What types of nonsampling error do you think this may lead to?

Determine whether the survey question is biased. If the question is biased, suggest a better wording.

Do you agree that the town’s ban on skateboarding in parks is unfair?