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Flashcards in Gather Data Deck (14)
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1
Q
what is stratified random sampling?
A
dividing the population into groups, then taking a random sample from each group
2
Q
why isn't a stratified sample the same as a simple random sample?
A
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
3
Q
what is cluster sampling?
A
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
4
Q
What is a simple random sample?
A
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
5
Q
What is sampling error?
A
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.
6
Q
what is the difference between a parameter and a statistic?
A
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
7
Q
what is a biased sample?
A
A sample that is not representative of the population.
8
Q
What is non response bias?
A
When you sample by sending out a survey, or questionnaire, and some people do not respond
9
Q
What is voluntary response bias, and why is it biased?
A
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
10
Q
What is response bias?
A
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
11
Q
What are two differences between observational studies and experiments?
A
In experiments, treatments are applied. Only with experiments can you infer causation
12
Q
What are factors, also called explanatory variables in an experiment?
A
What is being manipulated, such as what kind of feed is being fed to the chickens, or the type of drug being given
13
Q
What is the response variable?
A
What you are measuring at the end of the experiment. Examples might be blood pressure, cholesterol level, or the weight of a dog.
14
Q
Where does the "random" occur in an experiment?
A
Not in choosing the subjects, they are usually volunteers! The randomization occurs in the assignment of treatments.