Homework 1.2

What is a​ census, what is a​ sample, and what is the difference between​ them?

A census is the collection of data from every member of the​ population, but a sample is the collection of data from only a part of the population.

What is a representative​ sample, and why is it​ important?

A representative sample is a sample in which the relevant characteristics of the sample members are generally the same as the characteristics of the population. This type of sample is important because only a representative sample can be used to make trustworthy inferences about the population.

A​ magazine, which does not accept free products or advertising from​ anyone, prints a review of new cars. Are there sources of bias in this​ situation?

There do not appear to be any sources of bias.

A company hires independent university scientists to determine whether its​ new, genetically engineered soybean poses any threat to the environment. Are there sources of bias in this​ situation?

There does appear to be a source of bias.

A pollster conducts a research project about how adult Chinese pay their bills. She hands her survey to 23 people in her office building. Identify the sample, population, and sampling method.

- Sample: The 23 people in her office who completed the survey - Population: All Chinese adults - Sampling method: Convenience sampling - most likely not representative of the population

An engineering student measures the strength of fingers used to press the buttons on a newly designed garage door opener by testing a friend's family members. What type of sampling is used?

- Sample: convenience sampling - The procedure is likely to be​ biased, because it consists of family members likely to have similar physical characteristics and exercise habits.

In a Gallop poll of 1,070 randomly selected American sportsmen, 89% said that cloning of humans shouldn't be allowed. Identify the sample, population, and sampling method.

- Sample: the 1,070 randomly selected American sportsmen - Population: all american sportsmen - Sampling method: Random - The sample is fairly large and random. Assuming it was obtained by a reputable firm, the sample is likely to be representative of the population

A college dean obtains an alphabetical list of all full-time students at her college and she selects every 18th name on that list and surveys those students to find the amount of student debt incurred by each of them. She uses the results to estimate the average (mean) amount of student debt incurred by college students in the United States. What type of sampling is used?

- Sampling method: Systematic sampling - The procedure is likely to yield a biased sample because the students she surveys are all from the same school.

A famous magazine chooses its "most-talented actors" by compiling responses from readers who mail in a survey printed in the magazine. What type of sampling is used?

- Sampling method: convenience sampling - The procedure is likely to yield a biased sample because it is a​ self-selected sample and consists of those with strong feelings about the topic.

What is a biased​ sample, and what is a major problem with​ it?

A biased sample is a sample where the members of the sample differ in some specific way from the members of the general population. The major problem with a biased sample is that the results obtained from a biased sample are likely to be misleading.