sampling techniques Flashcards
what are the types of samplings?
- random
- systematic
- stratified
- opportunities
- volunteer
what is random sampling?
sophisticated form of sampling where all members of the target population have an equal chance of being selected
• also used with random allocation of p’s to condition when using independent groups design
how is random sampling done?
• a list of all members are obtained
• name are assigned a number
• sample is generated through the use of a lottery method (computer based randomiser set with random parameters)
what are the + and - of random sampling?
(+)
• prevents bias
(-)
• time consuming
• may be ungeneralisable eg more females than males
what is systematic sampling?
• p’s are chosen mathematically
• done by taking every nth person in the sampling frame for the sample
how is systematic sampling down?
• list the sampling frame into alphabetical order then select the every nth number
• keep selecting until the sample is complete
what are the + and - of systematic sampling?
(+)
• random - less than random
• prevents bias
(-)
• time consuming
• not easy to obtain
• needs consent
what is stratified sampling?
• sampling frame is divided into groups (strata) that the researcher wants to make sure are represented
• a certain number of p’s are selected form these groups so that they are proportionally represented in the sample
how is stratified sampling done?
% of strata x sample
what is the + and - of stratified sampling?
(+)
• high representative
(-)
• time consuming
what is opportunity sampling?
• consists of p’s who have been chosen because they are convenient
• meaning they might have been selected because:
- they have actively volunteered
- they are in the locality
- they are known to the researcher
what are the + and - of opportunity sampling?
(+)
• not time consuming
(-)
• unrepresentative (certain type of people)
what is volunteer sampling?
• self selecting sample p’s who have volunteered to take part
what are the + and - of volunteer?
(+)
- quick
- minimal effort
(-)
- unrepresentative
- volunteer bias (eager to please)
what is a sample?
the selected sample for the research
