What is an observational study?
A study in which individuals are observed and variables of interest are measured, but there is no attempt to influence the responses.
What is the purpose of an observational study?
To describe and compare existing groups or situations.
What is an experiment?
A study in which a treatment is deliberately imposed on individuals in order to record their responses.
What is the purpose of an experiment?
To study whether the treatment cause a change in response.
True or false?: Observational studies often fail to show causality because the explanatory variable is confounded with lurking variables.
True.
What is a sampling design?
A sampling design describes how a sample is chosen from the population.
What is a statistical inference?
The process of drawing conclusions about a population on the basis of sample data.
True or false?: Accurate inferences can be made for any reasonable sample size and data variability.
True.
How does large sample size typically affect statistical inferences?
A large sample size can lead to more precise inferences.
How does a sample size with low variability typically affect statistical inferences?
A sample size with low variability can lead to more precise inferences.
What does it mean for a study to be biased?
A study is biased when it systematically favors certain outcomes.
What are examples of poor sampling?
Convenience sampling and voluntary response samples.
What is a probability sample?
A sample chosen by chance; random selection of individuals.
What are examples of probability samples?
Simple random sampling, stratified random sampling, and multistage random sampling.
What is convenience sampling?
A convenience sample is one that chooses individuals close at hand.
what is a voluntary response sample?
A sample in which individuals individuals choose whether or not they want to participate in the study.
What is simple random sampling?
A sample in which every set of n individuals from the population has an equal chance to be the sample chosen for the study.
What is a sample survey?
An observational study that relies on a random sample drawn from the entire population of interest.
What is undercoverage?
A form of selection bias that occurs when some groups in the larger population are left out of the process of sample selection.
What is nonresponse?
Nonresponse occurs when a selected individual in a sample cannot be contacted or refuses to participate.
True or false?: Sample surveys often suffer from undercoverage, but rarely suffer from nonresponse.
False. Both undercoverage and nonresponse occurs often in sample surveys.
What is a case-control study?
A study in which a random sample of individuals with a condition is compared with a random sample of individuals without the condition.
What is a cohort study?
A study in which subjects sharing a common demographic are enrolled and observed at regular intervals over an extended period of time.
What is a stratified random sample?
A sample in which the population was divided into groups based on shared characteristics and each group is sampled individually.
