Sampling Flashcards
A01 Define
Population
Group of people from where sample is drawn
Define
Sample
Group of people who take part in research.
* Sample is drawn from (Target) Population & is representative of that population so that generalisation of findings become possible
What is a target population
Subset of general population
A01
What is random sampling
- Each member of target population has equal chance of being in sample
How to conduct: - Each member of target population assigned number
- Random number generator/lottery method used to randomly choose participant
A03
What is a strength of Random sampling
No researcher bias-researcher has no influence of who is picked
means extraneous & cofounding variabales equally divied between groups-enhancing internal validity
What is a limitation of Random sampling
Time consuming & difficlut to get list of members of target population
*by chance participants could produce unrepresentative sample e.g too fewer memebers of one gender
What is systematic sampling
Participants are chosen from a list of the target population
Every nth participant is chosen to form the sample
(e.g every 5th,10th or 100th name)
Process continues until sample required
What is a strength of systematic sampling
- Avoids researcher bias as researcher cannot choose participants they want in sample-fairly representative
- If there is existing list of target population
What is a limitation of systematic sampling
- Not truly unbiased
What is a opportunity sample
Researchers directly asks available memeber of traget population
How to conduct:
1. Researchers directly asks memeber from target population to take part in research
What is a strength of opportunity sample
Easy method of recruitment-reducing time it takes to conduct research & reducing cost involved
What is a limitation of Opportunity sample
- Not representative of target population
as its drawn from specific area - Researcher bias-as can control who they want to select
Suffers from 2 forms o f bias
What is a Volunteer sample
involves self selection-Participants select themselves to be part of sample
How to condcut:
Advertisement are placed -advert in newspaper or online
What is a strength of Volunteer sample
Quick access to willing participants reducing time & cost
*
What is a limitation of Volunteer sample
Sample not generalisable to target population- volunteer bias
those who take part likely have diff characteristics to target population-affects generalisability
What is stratfied sampling
By selecting from within strata, Characteristics of participants within the sample are in the same proportion as found within target population
How to conduct:
1. Strata/subgroups identified along with the proportion of target population E.g gender, ethnicity
2. Random sampling used to select number of participants required from within each stratum
What is a strength of Stratified sampling
Sample is representative of larger target population
means results found in the sample should be generalised to target population
As participants randomly chosen from within each stratum this avoids researcher bias
What is a limitation of stratified sampling
Time consuming to establish strata & randomly select from each stratum
