Sampling Flashcards
What is Sampling?
A technique for selecting a representative subgroup of a larger population, accurately reflecting the distribution of a variable, to estimate something about it. (Person, Place, Time)
What is a Population?
- A group of people having one or more common characteristics living in a specific geographical location.
What is a Sampling Frame?
- The actual list of individuals that the sample will be drawn from.
- Needs to be complete and accurate; For the success of the study.
What are Sampling Units?
A single element or group of elements that are selected for a sample.
What is Sampling Variation?
The value can vary from sample to sample, depending on which sample is selected.
What is a Sampling Error?
- Arises out of random sampling.
- Statistical errors that arise when a sample does not represent the whole population.
Why do we need a sample?
- Save time and money.
- Unable to study all members of a population.
- Reduce bias.
- Measurements; better in sample than in entire population.
- Feasibility (Practicable)
How to sample?
In general, 2 requirements
- Sampling frame - available/develop one if not exist.
- Choose an appropriate sampling method to draw a sample from the sampling frame.
What are the Sampling Methods?
I. Probability sampling
- Every member of the target population has a known chance of being included in the sample.
II. Non-probability sampling
- The researcher selects samples based on their subjective judgment, rather than random sampling.
What is Simple Random Sampling?
(Type, Definition, Advantages, Disadvantages, Examples, How to do it[Techniques], and Select sample)
1 - Probability Sampling Method.
2 - Randomly selected subset of a population. (Equal Chance)
3 - Advantage
- Easy to do.
- Accurate representative.
- Removes all bias.
4 - Disadvantage
- Time Consuming
5 - Examples
-Pharmaceutical Patients (From a hospital record system.)
- Uni Students Selection.
6 - Techniques
- Lottery method
- Table of random numbers
7 - Selection;
- Define the population.
- Determine the desired sample size.
- List all members of the population or the potential subject.
What is Systematic Random Sampling? (Type, Definition, Advantages, Disadvantages, and Example.)
1- Probability Sampling Method
2- You sample every kth element from a population.
3 - Advantage
- Quick, Simplicity, and Convenience.
- Precision
4 - Disadvantage
- Over- or Under Representation.
- Risk of Data Manipulation.
5 - Example
- Every 25th name in a phone book.
What is Stratified Random Sampling? (Type, Definition, Advantages, Disadvantages, and Example.)
1 - Probability Sampling Method.
2 - Strata - Different Layers
- Population is divided into subpopulations and random samples are taken from each stratum (strata)
- Sample from each stratum should be proportional.
3 - Advantages
- Accurate
- Include sub-groups (Ensure representation of all groups of interest)
- Disadvantage
- Time Consuming
- Expensive
- Complex
- Examples
- Students from all grades (In a school study.)
- Ethnicity
What is Cluster (Area) Random Sampling?
(Type, Definition, Advantages, Disadvantages, Example, and Appropriate when)
1 - Probability Sampling Method.
2 - Researchers divide a population into smaller groups called clusters. They then form a sample by randomly selecting clusters.
3 - Advantage
- Quick.
- Less costly.
- Accurate.
4 - Disadvantages
- Biased samples
- High sampling error
- Examples
- Study the prevalence of obesity, health behaviour, or rare diseases across different communities or regions.
6 - Appropriate when;
- Can’t obtain a list of the members of the population.
- Have little knowledge of population characteristics.
- Population is scattered over a large geographic area.
What is Multistage Random Sampling?
(Types, Definition, Advantages, Disadvantages, Examples, and Stages)
1 - Profitable Sampling Method.
2 - An extension of Cluster Random Sampling.
- Draw a sample from a population using smaller and smaller groups (units) at each stage.
3 - Advantages
- Flexibility
- Cost-Effectiveness
4 - Disadvantages
- Subjectivity
- Less Accuracy
5 - Examples
- Study different eating habits in specific regions.
- Research firm (UK); A survey… dividing the country into counties and towns, and randomly selecting clusters from each.
6 - Stages
. Stage 1
Randomly sample clusters (schools).
. Stage 2
Randomly sample individuals from the schools selected.
What is Snowball Sampling? (Types, Definition, Advantages, Disadvantages, Examples, and Note)
1 - Non- Probability Sample.
2 - Have samples that have traits that are rare to find.
3 - Advantages
- Low cost
- Easy to implement
-Researchers can reach a particular population that would otherwise be difficult or impossible to reach.
4 - Disadvantages
- Sampling bias
- Not guaranteed to be a representative of the large population.
5 - Examples
- Exploring secret societies.
- Estimating the size of the problem of trafficking begins.
6 - Note
(Very difficult to collect primary data, unless authorised.)
What is Consecutive Sampling? (Types, Definition, Advantages, Disadvantages, and Examples)
1 - Non- Probability Sample.
2 -Every subject meeting the criteria of inclusion is selected until the required sample size is achieved.
Advantages
-Quick and Easy
-Efficiency
Disadvantages
-Sampling Bias
5 - Examples
- A researcher wants to analyze the effect of eating snacks with a soft drink.
6 - Technique
The researcher selects a sample, conducts research over time, collects results, and then moves on to another sample.
What is Purposive (Judgmental) Sampling? (Types, Definition, Advantages, Disadvantages, Examples, Technique)
1 - Non- Probability Sample.
2 - Criterion-based sampling.
- The researcher selects participants based on their qualifications or characteristics relevant to the study.
3 - Advantages
-Cost-effective
-Saves time
4 - Disadvantages
-Researcher bias
-Participants - Can manipulate the data being collected.
5 - Examples
- Buying patterns of high-end luxury cars; Select a sample of individuals who they believe are most likely to purchase a luxury car.
- A researcher wanting to know what it takes to graduate summa cum laude in college may only select individuals who graduated summa cum laude.
6 - Technique
- Often used in qualitative research technique - saves time and money by filtering out irrelevant responses without relying on random selection.??
What is Quota(Deliberate) Sampling?
(Types, Definition, Advantages, Disadvantages, and Examples)
1 - Non- Probability Sample.
2 - Participants are selected based on specific characteristics, that represent a population.
3 - Advantages
- Low cost
- Saves time
4 - Disadvantage
- Increase the risk of researcher bias.
- Not accurate.
5 - Examples
Uni; Conduct a survey on student satisfaction with campus life.
What is Convenience sampling? (Types, Definition, Advantages, Disadvantages, and Examples)
1 - Non-Probability Sample.
2 - Consists of people who are easily reached.
3 - Advantages
- Access data easily.
- Low cost.
- Large amount of qualitative info.
4 - Disadvantage
- Selection bias
- Over/Under representation of the population.
-Can’t generalise.
5 - Examples
- Interviewing people on the street.
-Online surveys
What are examples of Probability Sampling?
- Simple random sampling
- Stratified random sampling
- Systematic random sampling
- Cluster (area) random sampling
- Multistage random sampling
What are examples of Non-Probability Sampling?
- Deliberate (quota) sampling
- Convenience sampling
- Purposive (Judgment) sampling
- Snowball sampling
- Consecutive sampling
What is a Sample?
The specific group of individuals that you will collect data from.
Representative subgroup of the larger population.
Generalisation.
Must be similar to the population on characteristic being investigated.
What is the Sampling design process?
1 - Define pop
2 - Determine Sampling Frame
3 - Select Sampling Technique(s)
4 - Determine Sample Size
5 - Execute Sampling Process
