Types of Experiments/Sampling

Random 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