sampling Flashcards
sampling frame
which is a list of all
individuals belonging to the population
sampling design
describes exactly how to choose a sample from the
sampling frame
Non-probability samples
which are biased sampling designs
Probability samples,
which are unbiased sampling designs
In general, we classify sampling designs as:
* Non-probability samples, which are biased sampling designs
These designs over- or under-emphasize some characteristics of the population based
on the procedure used to select individuals for the sample.
* All individuals in the population do not have an equal chance of being sampled.
* As a result, the sample will likely not be representative.
- In general, we classify sampling designs as:
- Non-probability samples, which are biased sampling designs
- Probability samples, which are unbiased sampling designs
All individuals in the population have an equal chance of being sampled.
* This means that, on average, the sample will be representative of the population.
Biased Designs types
convience sampling and voltuary smapling
convenience sample
A convenience sample is a sample obtained by selecting individuals in
the population that are easiest to reach.
voluntary response sample
A voluntary response sample consists of the people who choose to
respond to a broad invitation
Unbiased Designs
* Today, we will present three common unbiased sampling designs
. Simple random sample (SRS)
2. Stratified random sample
3. Cluster sampling
Simple Random Sample (SRS)
selects
individuals from the sampling frame
through pure randomization.
* A SRS of size n consists of n individuals from
the population chosen in such a way that:
* (1) each individual has the same chance of
being selected
* (2) each combination of n individuals has equal
chance of being selected
The most likely result of a simple random
sample is a
The most likely result of a simple random
sample is a representative subset, as we
see in the example.
* However, just due to chance, it is possible
that we obtain a sample that is not
representative.
Stratified random sampling
eparates the population into mutually
exclusive groups (strata) and then draws simple random samples from
each stratum
Cluster Sampling
Although we cannot obtain a sampling frame that includes all
individuals in the population, we hope to be able to obtain a sampling
frame of mutually exclusive groups (called clusters) that include all
individuals in the sampling frame.
A cluster is believed to be a
A cluster is believed to be a representative group from the population, not
grouped by any feature believed to affect the variable of interest.