Flashcards in Gather Data Deck (14)
what is stratified random sampling?
dividing the population into groups, then taking a random sample from each group
why isn't a stratified sample the same as a simple random sample?
because each subgroup of the population is not equally likely to be chosen. For example, if UHS is our population and we stratify be grade, and take a random sample of 25 students from each grade, the subgroup made up of 100 seniors would never be chosen
what is cluster sampling?
Break the population into groups, or clusters, like, "all the classes that meet first block", randomly choose some of the clusters, then sample everyone in the chosen clusters
What is a simple random sample?
Randomly choosing your sample from the entire population. Example: put the name of every student at UHS in a large container, and reach in and pick 100 names
What is sampling error?
Not a mistake or an error! It just refers in the variability in sampling. If you take a random sample of 50 UHS students, you might find that 82% like pizza. If I take another simple random sample of 50 students, I might find that 93% of my sample like pizza.
what is the difference between a parameter and a statistic?
If you calculate the mean, or any other numerical summary, like median or standard deviation of an entire population, we call it a parameter. If we calculate the mean, or median, or standard deviation of a sample, we call it a statistic
what is a biased sample?
A sample that is not representative of the population.
What is non response bias?
When you sample by sending out a survey, or questionnaire, and some people do not respond
What is voluntary response bias, and why is it biased?
When you sample by inviting people to respond, like on a talk show. It may be biased because often only people with strong opinions will respond
What is response bias?
Bias due to the wording. People may not want to admit certain things, like their weight or drug use, or the wording may lead them to a certain response
What are two differences between observational studies and experiments?
In experiments, treatments are applied. Only with experiments can you infer causation
What are factors, also called explanatory variables in an experiment?
What is being manipulated, such as what kind of feed is being fed to the chickens, or the type of drug being given
What is the response variable?
What you are measuring at the end of the experiment. Examples might be blood pressure, cholesterol level, or the weight of a dog.