Experimental Methods

• Qualitative data


  Data in the form of text/pictures (transcripts, field notes & sometimes pictures)
• Quantitative data


  Data in the form of numbers
• Qualitative data is naturally occurring & rich data (open ended, i.e. open for interpretation)
• Analysis of qualitative data is often difficult & time consuming: no single approach to data analysis
• Qualitative research often involves fewer participants (non-probability sampling)- difficult to generalise
• Analysis of quantitative data is relatively easy- statistical tests
• Quantitative research is easier to use data from many participants & aim is often to generalise of findings to populations
• Both qualitative and quantitative approaches are equally valuable and their use will depend on the aims and objectives of an investigation
• Behaviour is often the result of complex social, cultural, cognitive as well as biological interactions, a combination of approaches to researching behaviour is not only inevitable, but desirable
• Research methods that often yield qualitative data


  • Case Studies
  • Naturalistic Observations
  • Interviews
• Research methods that often yield quantitative data


  • Lab Experiments
  • Field Experiments
  • Natural Experiments
  • Quasi Experiments
  • Correlational Research
  • Surveys
• Surveys that include open ended questions will yield qualitative data
• In some naturalistic observations, psychologists do numerical counts of particular behaviours therefore producing quantitative data
• Experimental method


  Direct way to test a hypothesis to find a cause and effect relationship between factors
• Experimental method


  Manipulates one or more factors to observe their effect on some behavior or mental process while controlling other relevant factors
• Independent variable


  The factor that is manipulated by the researcher, hypothesised to cause an effect on another variable
• Dependent variable


  The observed and measured factor, hypothesised to be affected
• Experimental condition


  The condition that exposes the subjects to the independent variable
• Control condition


  The condition that serves as a contrast or comparison to the experimental condition, the subjects are not exposed to the independent variable
• Extraneous variables


  All variables, which are not the independent variable, but could affect the results (DV) of the experiment
• Types of extraneous variables


  • Situational variables
  • Participant variables
  • Experimenter effects
  • Demand characteristics
• Control variables


  Experimental controls that researchers use to minimise the chances that variables other than the independent variable have impacted the dependent variable
• Where experiments are highly controlled we can say they have high internal validity
• Internal validity


  Whether results obtained were due to the manipulation of the IV rather than any other factors such as extraneous variables
• Experimental hypothesis


  A statement that is testable and falsifiable based on the results of an experiment or observation, stating the relationship between two or more factors (variables)
• One-tailed hypothesis


  States which direction the results will go in and usually contains words like 'more', 'better', 'faster'
• Two-tailed hypothesis


  Predicts that the IV will impact the DV but it does not include a prediction of the direction the results will go in, tends to include terms like "there will be a difference between…" or "have an effect on"
• Null hypothesis


  A prediction that the independent variable will have no effect on the dependent variable
• Operationalising variables


  Clearly defining the independent variable and the dependent variable, including how they will be manipulated and measured
• True experiment


  The researcher manipulates the independent variable, there are at least two conditions that are compared, and allocation to conditions is done randomly
• Laboratory experiment


  A type of true experiment conducted in a controlled environment with a highly standardised procedure
• Field experiment


  A type of true experiment conducted in the participants' natural environment, with some degree of control but less than a lab
• Quasi-experiment


  Not a true experiment, where assignment of participants to conditions cannot be made at random for practical or ethical reasons
• Natural experiment


  A special type of quasi-experiment where the independent variable is environmental in nature and outside of the control of the researcher
• Pre-test/post-test design


  An experiment where the dependent variable is measured both before and after the independent variable is introduced