Types of Experiments/Sampling

Random Sampling

Every member of the target population has an equal chance of being in any group

Stratified sampling

More theory driven
The sample has to reflect essential characteristics for your experiment
The characteristics are then studied by the distribution of these characteristics
The participants are then recruited in a way that keeps the proportion of the characteristics the same

Convenience Sampling

Participants are recruited based on how easily available they are
Technique of choice when resources or time is limited

Self Selected sampling

Recruiting volunteers
EG: Advertising the experiment to get more recruits
Easy way to get participants

Purposive sample

Main characteristics are defined in advance
EG:
Research on HS teachers would define the sample in advance by only choosing HS Teachers

Snowball sample

When participants invite other people to join the experiment
Good for recruiting populations such as druggies or gang members

Independent measures design

Random allocation of participants into groups and the comparison between those groups
The participants are randomly assigned to the experimental and controlled groups
The only thing that is different in these groups is the IV

Matched pairs design

Similar to independent measures
No random allocation, but matching allocation to form groups

Repeated measures design

Goal is to compare conditions instead of the group
Same group of participants are exposed to different conditions
The results of the conditions is what’s being measured
Can be affected by order effects
What IV comes first and how that will affect the groups reaction after the first condition
Counterbalancing is used to combat order effects
The order of the conditions are reversed

Field experiment

Experiments done under a natural setting
Less control over variables

True experiment

IV is manipulated and DV is measured under really controlled conditions
Participants are randomly assigned to the conditions

Quasi experiment

No IV is manipulated
Participants aren;’t randomly selected to conditions
The only thing that separates the participants are their traits
EG: Banker, teacher

Natural Experiments

An experiment that is the result of a naturally occurring event
There is no control over the IV as it naturally occurs in real life
EG:
A test to see the amount of heart-attacks before and after a smoking ban was set