sampling

• selecting a sample should be done carefully
• part that you want to study - target group
• sample - when you can't include everyone from target group
• sample should be representiatitive
• sample that is unrepresentative is biased and can't be generalised
• random sampling - every member has an equal chance of being picked
• opportunity sampling - whoever is there and willing to take part
• random pro - fair
• random con - doesn't guarentee representiatitivness
• opportunity pro - quick and practical
• opportunity con - unlikely to be representiatitive
• volunteer - volutneer through ads or posters
• volunter pro - more people
• volutneer cons - unlikely to be representiaitive
• systematic sampling - nth name from sampling is taken
• systematic pros - simple and effective
• systematic cons - not representiatitive
• stratified - all the important subgroups have 2 taken from each
• stratified pro - fair and representiatitive
• stratified cons - takes lots of time and money
• hawthorne effect - change due to being observed
• demand characteristics - please me and screw you effect
• social desirability bias - show theirself in the best possible light
• placebo effect - fake treatment can make people feel better
• double blind procedure - neither participant or experimenter knows who is getting what
• researcher bias - can influence the study
• investigator effects - anythign researcher does that changes behaviour