Probability Sampling:
What is Probability Sampling?
- Probability sampling: In this
Sampling every unit in the population/Set has a
equal chance (greater than zero) of being selected
in the sample, and this probability can be accurately
determined
- Non-probability sampling: In this
Sampling every unit in the population/Set has a
Unequal chance (greater than zero) of being
selected in the sample, and this probability can be accurately
determined.Here some units may have Zero probability of being
selected at all.
Types of Probability Sampling
- Simple random sampling: In a simple random
sample of a given size, all elements of the Set are given an equal
probability. Each element of the Set thus has an equal probability
of selection.The Set is not subdivided or
partitioned.
- Stratified Random Sampling When the population
embraces a number of distinct categories, the frame can be
organized by these categories into separate "strata." Each stratum
is then sampled as an independent sub-population, out of which
individual elements can be randomly selected
- Systematic Sampling Systematic sampling (also
known as interval sampling) relies on arranging the study
population according to some ordering scheme and then selecting
elements at regular intervals through that ordered
list.Systematic sampling involves a random start and then proceeds
with the selection of every kth element from then
onwards
- Cluster Random Sampling is a way to randomly
select participants from a list that is too large for simple random
sampling. For example, if you wanted to choose 1000 participants
from the entire population of the U.S., it is likely impossible to
get a complete list of everyone. Instead, the researcher randomly
selects areas (i.e. cities or counties) and randomly selects from
within those boundaries.
- Multi-Stage Random sampling uses a combination
of techniques.
Advantages and Disadvantages
Each probability sampling method has its own unique advantages
and disadvantages.
Advantages
- Cluster sampling: convenience and ease of
use.
- Simple random sampling: creates samples that
are highly representative of the population.
- Stratified random sampling: creates strata or
layers that are highly representative of strata or layers in the
population.
- Systematic sampling: creates samples that are
highly representative of the population, without the need for a
random number generator.
Disadvantages
- Cluster sampling: might not work well if unit
members are not homogeneous (i.e. if they are different from each
other).
- Simple random sampling: tedious and time
consuming, especially when creating larger samples.
- Stratified random sampling: tedious and time
consuming, especially when creating larger samples.
- Systematic sampling: not as random as simple
random sampling,