Psychology - research methods

• Hypotheses

  Statements made by researchers to show what they predict their findings will be before carrying out a study
• Null hypothesis

  A prediction that suggests there will be no pattern in the results
• Null hypothesis

  • There will be no significant difference in the number of people that pick up litter for someone in a milkman uniform and someone not in a uniform
  • There will be no significant correlation between people's neuroticism scores and how many crimes they have committed in the past year
• Alternative hypothesis

  An alternative to the null hypothesis that does predict some kind of pattern in results
• Alternative hypothesis


  • There will be a significant difference in the number of children that show the ability to conserve depending on whether they are four years old or seven years old
  • There will be a significant correlation between people's psychoticism scores and how many crimes they have committed in the past year
• Variables

  Things that can change in studies
• Independent variable (IV)

  The variable that is manipulated or changed by the researcher
• Dependent variable (DV)

  The variable that is measured and is predicted to be affected by the IV
• Co-variables

  Variables that are related to each other but one does not necessarily affect the other
• Extraneous variables

  Other factors that can affect the outcome of a study if not controlled
• Standardisation

  The process of keeping extraneous variables the same so they do not vary
• Repeated measures design


  • Participants take part in both (or all) conditions
  • There are no participant variables so any differences between conditions cannot be put down to using different participants
  • It is more cost effective as the same participants can be used for both conditions
• Independent measures design

  • Participants take part in only one condition
  • There are no order effects as participants cannot get better through practice or worse through boredom/fatigue
  • The task can remain the same between conditions as the participants are not the same
• Target population


  The group of people that psychologists are investigating
• Sampling

  Selecting a smaller group to study that represents the rest of the population
• Sample size

  The larger the sample, the greater the proportion of the target population that is being studied
• Sampling methods

  • Random sample
  • Opportunity sample
  • Self-selected sample
• Ethical guidelines


  A set of recommendations that psychologists should try to follow when carrying out research
• Ethical issues

  • Lack of informed consent
  • Protection of participants from psychological harm
  • Deception
• Debriefing

  A conversation between researchers and participants that happens at the end of a study
• Confidentiality


  The act of keeping something secret or private
• Headings of the British Psychological Society's code of ethics and conduct

  • Respect
  • Competence
  • Responsibility
  • Integrity
• Experiments always have an independent variable and dependent variable, and then other extraneous variables which are controlled
• Experiments

  • In a laboratory experiment the environment is controlled
  • In a field experiment a natural environment is used instead
  • In a natural experiment the IV is not directly manipulated by the experiment but instead is something that would change naturally (or in real life) anyway
• Strengths of experiments

  • Cause and effect can be established with some degree of reliability
  • The method is very objective because it is so highly controlled
  • Laboratory experiments are the most reliable form of experiment as there are so few extraneous variables
  • Field experiments have high ecological validity as participants are experimented on in their normal setting
  • Natural experiments allow experimenters to investigate IVs that it would be impossible or difficult to set up
• Weaknesses of experiments

  • Experiments tend to have low construct validity as the DV often has to be measured in a narrow way
  • Experiments often suffer from demand characteristics especially if the participants are aware they are being investigated
  • Laboratory experiments often use artificial environments that do not relate to real life (have low ecological validity)
  • Field experiments have more extraneous variables than laboratory experiments, meaning they are not as reliable at establishing cause and effect
  • Natural experiments may have other variables that change at the same time as the IV