Unit 12 Experimental Design Flashcards
What’s a population?
a population is the entire group of individuals whom you want to describe.
What’s a sample?
a sample is a smaller group of individuals you select FROM the population
What’s the sampling frame?
the sampling frame is a list of individuals from the population of interest from which the sample is drawn.
What happens if
- the sampling frame is NOT equal to the population of interest
- and is different from the population in some way that may affect the response variable?
Then the sample will be BIASED in some way.
When is a sample biased?
- the sampling frame is NOT equal to the population of interest
- and the sampling frame is different from the population in some way that may affect the response variable
What’s sampling variability?
sampling variability is the natural tendency of probability samples to vary.
Is sampling variability an error?
NO! sampling variability is not an error.
If sampling variability isn’t an error, then what is it?
sampling variability is the result of properly applied random sampling techniques.
What’s the sample size?
the sample size is the number of individuals you select from your sampling frame.
does the size of the population dictate the size of the sample?
NO!
What dictates the size of the sample?
ten percent rule dictates the size of the sample
What’s the ten percent (10%) rule?
the sample size should not be bigger than 10% of the population size.
What’s a census?
a census is the sample that’s the size of the entire population.
What’s a parameter?
a parameter is a number that describes an aspect of the population.
Do we know the parameter of a population?
No, we usually do not know the true value of a parameter, so we have to estimate it.
What’s a statistic?
a statistic is a number than describes an aspect of the SAMPLE DATA.
What do we use statistics for?
we use statistics to ESTIMATE values in the POPULATION.
What’s a sampling design?
a sampling design is the method we use to select the sample for a study.
What do all appropriate statistical sampling designs include?
all appropriate statistical sampling designs include the idea that chance, rather than choice, is used to select the sample.
What’re poor methods of selecting a sample? (2)
poor methods of selecting a sample:
- voluntary response sampling
- convenience sampling
What’s voluntary response sampling?
A voluntary response sample is a sample made up of volunteers.
What’s convenience sampling?
Convenience sampling is when you select subjects that’s close and convenient for you to sample
What’s the best defense against systematic errors in way that the data represents the population?
RANDOMIZATION is the best defense against systematic errors in way that the data represents the population.
What’re the appropriate selection methods?
appropriate selection methods:
- simple random sampling
- systematic random sampling
- stratified random sampling
- cluster sampling