Psychology - Experiments


Designing and understanding experiments

  • Experiment - a research method which measures participants' performance in two or more conditions
  • Experimental (participant) design - the way that participants are used in different conditions in an experiment
  • Independent groups design - different participants are used in each condition in an experiment
  • Control group - a group that does not receive an experimental condition to provide a baseline on which to compare those participants who do experience a condition of the experiment
  • Extraneous variables - any variables that might affect the results of the study that might not be controlled 
  • Independent variable - the factor which is changed by the researcher in an experiment to make two or more conditions
  • Dependent variable - the factor which is measured in an experiment
  • Repeated measures design - the same participants are used in all the conditions in an experiment
  • Hypothesis - a testable statement of the difference between the conditions in an experiment, describing how the independent variable will affect the dependent variable
  • Controls - ways to keep variable constant in all conditions of an experiment
    • An experiment is a way to find out whether one factor affects another
    • Sometimes experiments use repeated measures where participants need to participate in all conditions of the experiment, while others use independent measures where participants only participate in one
    • Hypotheses are written to say what an experimenter expects will happen in an experiment and always operationalise the independent variable and dependent variable and say how the independent variable will affect the dependent variable
    • The controls are what the experimenter does to keep variables the same in all conditions

Dealing with descriptive statistics

  • Descriptive statistics - ways to summarise results from a study
  • Mean - an average that is calculated by adding up all of the scores in a set and dividing by the number of scores
  • Median - an average that is the middle number in a set of scores where they are put in order from smallest to largest
  • Mode - an average that is the most common score or response in a set
  • Range - a way to show how spread out a set of results is by looking at the biggest and smallest scores
    • Averages tell us how most people responded and this gives us a general picture of the findings
    • Different kinds of experiments produce different kinds of data and for each kind of data there is an average

The ethics of psychological research

  • Psychologists are bound by a strict set of ethical guidelines that are regulated by the British Psychological Society (BPS) and their Code of Conduct, to help psychologists conduct their research in a way that will meet ethical guidelines
  • These guidelines help to protect participants of psychological research and make sure that the research conducted is carefully considered
  • Ethical issues - potential psychological or physical risks for people in experiments
  • Ethical guidelines - advice to help psychologists solve ethical issues
    • Wondering what will happen in your experiment, being concerned about how


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