Sampling Methods Flashcards
Ensures every member of the population has an equal chance of selection.
Purpose of Simple random sampling :
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How is simple random sampling carried out ?
Number each member of the population (or sampling frame) from 1 to ๐
Use a random number generator or random number table to select ๐ distinct numbers.
The corresponding members become the sample.
purpose of systematic sampling
Spreads the sample evenly over the population list, which can help avoid clustering.
More practical than simple random sampling when dealing with an ordered list.
How is systematic sampling carried out?
Arrange the population in a list (e.g., alphabetically, chronologically).
Decide on a sample size ๐. Calculate the sampling interval
Pick a random starting point between 1 and k
Select every k-th item after that (e.g., if starting point is 3 and k = 5 select 8,11,14..
purpose of stratified sampling
Ensures all relevant groups are represented proportionally in the sample.
how is stratified sampling carried out?
Divide the population into mutually exclusive strata (groups) based on some characteristic (e.g., age group, region, etc.).
Determine how many items to sample from each stratum in proportion to that stratumโs size in the population.
Within each stratum, choose items using simple random (or sometimes systematic) sampling
purpose of quota sampling
Quickly ensures that specific subgroups of interest are included.
Commonly used in market research and opinion polling when time or strict sampling frames are not easily available.
purpose of opportunity sampling
Used when time and resources are limited, or a quick snapshot is needed.
Not intended to be representative, but can be helpful for a preliminary check or pilot study.
how is opportunity sampling carried out?
Select items or participants that are the most readily available (e.g., the first people you encounter, or the first rows in a data set).
No formal random procedure is used.
How is quota sampling carried out?
The researcher decides on quotas for certain groups (e.g., 10 men and 10 women, or 5 items from each product category).
The researcher then actively selects (non-randomly) participants/items until each quota is fulfilled
what is the purpose of cluster sampling?
Reduces cost and time when the population is widely scattered.
often used in large-scale surveys where listing/visiting every single member is impractical.
How is cluster sampling carried out ?
The population is divided into clusters (often geographically).
A random selection of clusters is chosen.
Either all members of selected clusters are used, or a further random sample is taken within each chosen cluster.
