Sampling Methods
What's the difference between a convenience and simple random sample?
A convenience sample selects participants who are easy to reach, while a simple random sample (SRS) gives every individual in the population an equal chance of being selected.
What is response bias and how does it affect surveys?
Response bias occurs when participants provide inaccurate or false answers, often due to the wording of questions or social desirability, which can skew survey results.
How would you use a random number generator to select a sample?
Label each individual in the population with a number, then use a random number generator to pick numbers. Select the individuals corresponding to those numbers for your sample.
What does each dot on a dot plot represent?
Each dot represents the average value from a single sample.
What is the problem with surveying only landlines?
Many people, especially younger individuals, no longer use landlines, leading to under coverage of certain population groups.
Why is a larger sample size better?
A larger sample size reduces sampling variability, leading to estimates that are more likely to be closer to the true population parameters.
How does undercoverage lead to bias?
Undercoverage occurs when some groups in the population are left out of the sample, leading to results that do not represent the entire population.
Describe how you could take a random sample using slips of paper.
Write each individual's name on a slip of paper, place the slips in a hat, mix them, and then randomly select slips to form your sample.
How does the dot plot of a larger sample compare to a smaller one?
The dot plot for a large sample will have less variability, meaning the dots will be closer together, indicating more consistent estimates.
What was the problem with the Literary Digest Poll?
The poll suffered from under coverage because it only sent ballots to subscribers, car owners, and telephone owners, leaving out lower-income individuals who were more likely to support Roosevelt
What is sampling variability?
Sampling variability refers to the fact that different random samples can produce different results. Larger samples reduce this variability.
How does nonresponse bias affect surveys?
Nonresponse bias occurs when a significant number of selected participants do not respond, and those who do respond may differ systematically from those who do not, leading to biased results.
How does increasing the sample size reduce variability?
Increasing the sample size decreases sampling variability, which means the results of the sample are more likely to be close to the true population parameter.
How does sampling variability affect the results of different samples?
Sampling variability means different samples will produce different estimates of a population parameter. The amount of variability decreases with larger samples.
How does a poorly worded question create bias?
A poorly worded question can confuse respondents or lead them to answer in a specific way, introducing response bias.
What's the difference between a sample statistic and a population parameter?
A sample statistic is a value calculated from a sample that estimates a population parameter, which is a value that describes the entire population.
How did Boy Scout Peter's uniform introduce response bias?
People might feel pressured to support the Boy Scouts when Peter is in uniform, even if they do not, leading to response bias.
Why do researchers follow up with nonrespondents?
Following up with nonrespondents helps reduce nonresponse bias by increasing the participation rate, leading to more representative results.
How does a dot plot for a larger sample compare to one for a smaller sample?
A dot plot for a larger sample has less spread (lower variability) and produces estimates closer to the true population value.
Why might voluntary response surveys lead to biased results?
Voluntary response surveys tend to attract participants with strong opinions, particularly those who feel strongly about the topic, which can skey the results.
What is a simple random sample (SRS)?
A simple random sample (SRS) is a sample in which every individual in the population has an equal chance of being selected.
How could you avoid bias in a convenience sample?
Avoid bias by using random sampling methods, ensuring every individual in the population has an equal chance of being selected.
Why are sample results not always the same as the population proportion?
Due to sampling variability, different random samples can produce different results, so the sample proportion may not match the population proportion exactly.
How would you determine if the average word length of a song differs significantly from another sample?
Compare the average word length to the other sample's average using statistical tests to determine if the difference is significant or due to sampling variability.
Explain how response bias and nonresponse bias differ.
Response bias occurs when participants give inaccurate answers, while nonresponse bias happens when selected participants fail to respond, leading to a non-representative sample.