Populations, Samples and Sampling Flashcards
What is the definition of a statistical population?
The complete set of possible observations.
However, the population must be defined.
What is the definition of a statistical sample?
It is a set of observations taken from the population.
Why are samples usually taken?
Sampling the whole population would be impractical.
What does a good sample mean?
It will contain the information that will allow us to make conclusions about the population.
What is defined as an ideal sample?
- Representative of the population of interest.
- Should have equal chance of being sampled.
- Independence of sampling individuals.
- Sufficient size to draw conclusions about the population .
What are the 3 main sampling methods?
Random Sampling
Stratified Sampling
Cluster Sampling
What is Stratified Sampling?
Dividing a group into subgroups based on a particular characteristic.
What is non - probabilistic sampling?
This is known as non - random sampling. This means there is an unequal probability of selection.
Selection is subjective and the selection may be purely due to convenience.
What are 3 main types of selection bias?
Sampling Bias
Survivorship Bias
Self Selection Bias
What is sampling bias?
The sample is not reflective of the whole population.
What is survivorship bias?
Survivorship bias is a tendency to only focus on the survivors rather than everybody.
What is self - selection bias?
When individuals select themselves into a group, causing a biased sample with non-probability sampling
What is statistical inference?
Process of using analysis of sample data to draw conclusions about the population from which the sample was drawn.
