validity and reliability

• internal validity

  whether or not the research measured what it intended to measure - how successful the study has been controlling extraneous variables

  high internal validity - EVs were successfully controlled and the IV did change cause the change in the DV

  low internal validity - EVs weren't successfully controlled and may have affected the findings - any change in the DV may have been due to something other than the IV
• external validity 


  whether or not the findings can be generalised to the outside world - whether the research is representative of the people, places and times out in the real world

  ecological validity - can't generalise to real life settings

  population validity - can't generalise to other people in the target population

  temporal validity - can't generalise to modern times or modern world
• reliability


  consistency - study is reliable if when the study is replicated it produces similar results - can be tested using test-retest method which involves running the study once and then doing the same study again using exactly same participants and the same conditions - if research is reliable the results should be similar