experimental terms

• what is an experiment?

  a situation where unwanted influences are controlled or removed to see if a cause/effect process can be observed
• what is an independent variable?

  factor that is changed by the experimenter
• what is dependent variable?

  variable that is measured

  experimenter is looking to see if the variable has been affected by changing the independent variable
• extraneous variable


  unwanted factors e.g. location, type of participants (age, gender, intelligence) and type of researcher (gender, appearance)
• confounding variable


  variables left uncontrolled and do affect the results

  this means the researcher cannot be sure whether the results are due to the IV or the unwanted influences
• standardisation


  making sure the variables are kept constant
• Operationalistion


  defining the variables
• aims


  researchers purpose behind the study
• hypotheses


  prediction about what the researcher will find
• alternative hypothesis


  prediction that the researcher will find a result
• null hypothesis


  predicts nothing will be found
• non-directinal hypothesis


  when the researcher is unknown about the outcome
• directional hypothesis


  where the researcher is more confident about the outcome
• Opportunity sampling


  involves using whoever is available at the time

  advantage- saves time and effort

  disadvantage- can create a bias sample since there could be certain type of people around
• random sampling


  gives everyone in the population an equal chance of being selected e.g. putting everyone's name in a hat

  advantage- representative sample

  disadvantage- biased sample because the researcher might just pick out all males
• volunteer sampling


  putting up a notice asking for volunteers

  advantage- saves time and effort

  disadvantage- could lead to a bias sample because people may sign up because they are curious
• systematic sampling


  selecting every nth member of the population

  advantage- representative sample

  disadvantage- time consuming
• stratified sampling


  dividing the target group into sections

  advantage- representative sample

  disadvantage- time consuming
• independent group design


  each participant is randomly allocated to one of the groups by flipping a coin

  advantage- quick and easy

  disadvantage- bias may occur as the groups aren't equal
• matched group design


  participants are pre-tested on variables e.g. intelligence and then are paired up based on similar scores

  advantage- bias is being controlled

  disadvantage- time consuming
• repeated group design


  the participants take part in all the conditions

  advantage- reduces the chance of bias results

  disadvantage- participants may become bored or fatigued
• pilot studies


  small-scale version of the real study

  the main reason is to identify any problems in doing the study so any problems can be put right
• demand characteristics


  they occur when the participant attempts to work out what the study is about and then change their behaviour to please the researcher
• investigator effects


  these are to do with the way that the researcher themselves may bias the results

  what they say to the participants ad even unconscious biases can influence their findings
• single blind technique


  the participants are given a minimal amount of information about the nature of the study
• double blind technique


  both the participants and the researcher are unaware of how participants are meant to respond

  this is achieved by using a naive researcher who is not given any other information
• mode


  most common figure
• advantage of the mode

  less affected by extreme values
• disadvantage of the mode

  does not give any information about other figures in the number sequence
• median


  middle number when the numbers are put in order
• advantage of the median

  not affected by extreme values
• disadvantage of the median

  only based on one or two values in the number sequence
• mean


  when all the numbers are added together and the total is divided by the number of figures in the group
• advantage of the mean

  based on all the figures in the number sequence
• disadvantage of the mean

  it can be distorted by extreme figures
• range


  the difference between the lowest and highest number
• advantage of the range

  easy to calculate
• disadvantage of the range

  it can be affected by extreme scores
• standard deviation


  a measure of how far a sample of scores typically spreads out from the mean
• advantage of standard deviation

  it takes all the scores in the number sequence into account