Unit 1 Review for Test Flashcards
Identify the population and sample. A furniture maker buys hardwood in large batches. The supplier is supposed to dry the wood before shipping. The furniture maker chooses five pieces of wood from each batch and tests their moisture content.
Population: all the pieces of hardwood in a batch
Sample: The 5 pieces of wood that are selected
Identify the population and sample.
Each week the Gallup Poll questions a sample of about 1500 adult U.S residents to determine a national opinion on a wide variety of issues.
Population: all U.S. adult residents
Sample: the 1500 adults who actually respond to the survey
Identify the sampling method used and explain how the sampling method could lead to bias.
A farmer brings a juice company several crates of oranges each week. A company inspector looks at 10 oranges from the top of each crate before deciding whether to buy all the oranges.
Convenience sampling. This could lead the inspector to overestimate the quality of the oranges if the farmer puts the best oranges on top.
Identify the sampling method used and explain how the sampling method could lead to bias.
The ABC program Nightline once asked whether the United Nations should continue to have its headquarters in the United States. Viewers were invited to call one telephone number to respond “yes” and another for “No”. There was a charge for calling either number. More than 186,000 callers responded, 67% said no.
Voluntary response sampling. In this case those who are happy that the UN has its headquarters in the United States already have what they want and so are less likely to respond. The proportion who answered, “no”, in the sample is likely to be higher than the true proportion in the United States who would answer “no”.
What are the five accepted methods of sampling that lead to good data collection?
Simple Random Sample Stratified Random Sample Cluster Random Sample Systematic Random Sample Multi-stage Random Sample
What can go wrong with a sample that is done using a list of individuals in a population (like a phone list)?
Some members of the population cannot be chosen resulting in the UNDERCOVERAGE of those members
What is NONRESPONSE bias?
Bias that occurs when an individual chosen for the sample cant be contacted or refuses to participate
RESPONSE bias
When the gender, age, race, ethnicity, or behavior of the interviewer effects people’s responses and or when the respondents answers are effected by the interviewer
Identify the type of bias in the following survey.
An opinion poll asked 100 people randomly selected, “Should illegal immigrants be prosecuted and deported for being in the U.S. illegally, or shouldn’t they?
Poor wording of the question
Name the type of bias that could result and explain.
The sample is chosen at random from a telephone directory
Undercoverage - not everyone in the population may be listed in the directory.
Name the type of bias that could result and explain.
Some people cannot be contacted in five calls
Nonresponse bias - the people could not be contacted
Name the type of bias that could result and explain
Interviewers choose people walking by on the sidewalk to interview
Undercoverage that resulted from a convenience sample
A survey paid for by the makers of disposable diapers found that 84% of the sample opposed banning disposable diapers. Here is the question asked:
“It is estimated that disposable diapers account for less than 2% of the trash in today’s landfills. In contrast, beverage containers, third-class mail, and yard wastes are estimated to account for about 21% of the trash in landfills. Given this, in your opinion, would it be fair to ban disposable diapers?”
Explain how poor wording of the question could result in bias and specify whether the population proportion has been over or underestimated by the sample.
By making it sound as if the diapers are not a problem in the landfill, this question will result in fewer people suggesting that we should ban disposable diapers so it will underestimate the true proportion of the population who believe that we should ban disposable diapers.
Does reducing screen brightness increase battery life in a laptop computer? To find out, researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptop screens were left at the default setting - moderate brightness. Researchers then measured how long each machine’s battery lasted. Is this an observational study or an experiment? Justify your answer.
This is an experiment because a treatment, brightness adjustment, was applied to the laptops.
According to an ABC news article, “Teenagers who eat with their families at least five times a week are more likely to get better grades in school”. This finding was based on a sample survey conducted by researchers at Columbia University. Is this an observational study or an experiment? Justify your answer.
This is an observational study because there is not a treatment applied to the teenagers.
