Sampling Flashcards
what is a target population
every member of the group the investigator plans to study
what is a sample
a smaller group of people from the target population that are used to make judgements on the whole target population
what is random sampling
when each member of the target population has a mathematically equal chance of being in the experimenter’s sample
strengths of a random sample
- avoids researcher bias as they cannot choose which participants are in the sample
limitations of a random sample
- could produce an unrepresentative sample
- people can say no to taking part meaning it can become time consuming
how is a random sample carried out
names could be placed into a computer database and the number required for the sample be selected
what is systematic sampling
participants are chosen from a list of the target population
strengths of systematic sampling
- avoids researcher bias
- if there is an existing list of the target population it is quick
- list is easy to make if target population is small
limitations of systematic sampling
- could produce an unrepresentative sample
- if the target population is very large creating the list would be difficult
how to carry out systematic sampling
from the list of the entire target population (sampling frame) a system like every nth person would be selected for the sample
what is opportunity sampling
using those that are available at the time of testing by directly asking available members of the target population and adding those that are to the sample until the number for the sample is met
strengths of opportunity sampling
- fastest way to get a sample
- less organising
- specific groups can be targeted
limitations of opportunity sampling
- researcher bias as specific people can be targeted
