Sampling Flashcards
what is a population
a group of people who are the focus of the researcher interest
what is a sample
a group of people who take part in a research investigation
- sample drawn form a target population and is representative of the population
what is a random sample
All members of a target population have an equal chance of being selected
1. list all members of the target population
2. all members assigned a number
3. sample selected though a lottery method
what is a systematic sample
where every nth member of the population is selected
- a sampling frame is produced (list of people in the target population organised in some order)
1. identifies the strata that makes up the population
2. proportions needed for that sample are worked out
- participants that make up each stratum are selected using random sampling
what is an opportunity sample
- selects anyone who is willing and available
what is a volunteer sample
participant selects themselves to be a part of the sample
evaluation of random sample
- potentially unbiased
- confounding or extraneous variables are equally divided between the different groups enhancing the validity - difficult and time consuming to conduct as complete list of target population may be hard to obtain
- sample may still be unrepresentative as selection is random
evaluation of systematic sample
1 . objective
- once the system for selection had been established the researcher has no influence over who is chosen
2. time consuming
evaluation of a stratified sample
- representative sample
- generalisation is possible
evaluation of opportunity sample
- convenient
- less time costly as the list of whole population is not needed
-2. suffers form researcher bias
- unrepresentative of the target population
evaluation of a volunteer sample
- easy
- minimal input from the researcher
- less time consuming
- participants are more engaged as self selected - volunteer bias
- may attract a certain profile of a person
