Research methods

• Define experimental method

  The experimental method concerns the manipulation of an independent variable (IV) to have an effect on the dependent variable (DV) which is measured and stated in results
• What are 3 key features of an experiment

  1. manipulation of the IV

  2. Randomisation of participants

  3. Control of all variables (extraneous)
• What are the 4 types of experimental methods

  1. laboratory

  2. field

  3. quasi

  4. natural
• Laboratory experiment


  - conducted in a highly controlled environment

  - IV is manipulated to see the impact on the DV, whilst effects of other variables are minimised as much as possible
• Advantages of laboratory experiment

  - can be more certain about cause and effect due to high levels of control over confounding and extraneous variables

  - high external validity (the observed change in DV is due to the change in IV)

  - easy to replicate due to standardised procedures
• Disadvantages of laboratory experiment

  - lacks ecological validity due to the artificial nature of the procedure

  - lacks mundane realism so results cannot be generalised to real world

  - chance of demand characteristics as participants know they are in a study
• Field experiment


  IV is manipulated in a natural, more everyday setting e.g. in a school or supermarket
• Advantages of a field experiment

  - Higher mundane realism due to natural environment

  - High external validity (extent to which findings can be generalised beyond the application)

  - Reduced demand characteristics as participants don't know they are being studied
• Disadvantages of a field experiment

  - unethical as participant does not know they are being studied

  - lack of control of confounding and extraneous variables. This means cause and effect is more difficult to establish and precise application is not always possible
• Natural experiment


  The experimenter studied the effects of a naturally occurring IV. Participants may still be studied by a laboratory-type setting to see the effects, but the IV is not manipulated by the researcher.

  
  

  (IV is natural, not necessarily the setting)
• Advantages of a natural experiment

  - provide research opportunities that may not otherwise be possible for practical or ethical issues. The effects can be tested of factors that could not be manipulated by the researcher

  - high external validity because they involve the study of real world issues as the IV is naturally occurring.
• Disadvantages of a natural experiment

  - A naturally occurring event may only happen rarely, reducing research opportunities.

  - Participants cannot be randomly allocated to experimental conditions so it makes it harder to ascertain whether the IV affected the DV and also introducing the possibility of bias.

  - May not be possible to replicate due to lack of control over extraneous variables.
• Quasi experiment


  The IV is based on an existing difference between people e.g. gender, age, height etc.
• Advantages of a quasi experiment

  - can be tested under controlled, increasing the scientific credibility of the research

  
  

  - mainly depend on the setting which determines the ecological validation.
• Disadvantages of a quasi experiment

  - cannot randomly allocate participants to conditions so there may be confounding variables presented. This makes it harder to conclude that the IV caused the DV

  
  

  - mainly depend on the setting which determines the ecological validation.
• What is an independent variable


  What is changed or manipulated by the researcher and which is assumed to have a direct effect on the dependent variable
• What is the dependent variable


  This is what is measured and changes depending on the independent variable.
• What is the control variable


  variable that is kept the same
• What is an extraneous variable


  unwanted variables that could affect the DV, for this reason they must be controlled
• Examples of extraneous variables


  Participant variables

  Environmental variables

  Experimenter variables
• What is a confounding variable

  A type of extraneous variable that hasn't been controlled - they confound the results by affecting the DV
• Experimenter variables


  ways in which the researcher can influence the outcome of the research - these can be conscious or unconscious
• Examples of experimenter variables

  behaviour, gender, design of their experiment, interpretation of results
• Participant variables


  variables that are connected with the research participants
• Examples of participant variables


  intelligence, age, gender
• How can participant variables be avoided

  by using a repeated measures design or matched pairs or randomly allocated to groups.
• Environmental/situational variables


  variables connected to the research environment
• Examples of environmental/situational variables

  temperature, time of day, lighting
• How are environmental/situational variables avoided

  through standardisation - ensuring that the only thing that differs between the two conditions is the IV. This could include giving the participants the same instructions and treating them in exactly the same way
• Standardisation


  Using the exact same formalised procedures and instructions for every single participant involved - this minimise the effects of extraneous variables
• What is an aim

  - general statement made by the researcher which tells us what they plan on investigating

  - purpose of their study
• Where are aims developed from

  theories

  reading about other similar research
• What is a hypothesis

  A prediction of what the results will be through a precise and testable statement
• What are the 3 types of hypotheses

  1. directional

  2. non-directional

  3. null
• What is a directional hypothesis


  - states the direction of the impact of the IV on the DV

  
  

  e.g. The DV in the IV condition 1 is better/faster/less/fewer (etc) than the DV in the IV condition 2
• When do we tend to use a directional hypothesis

  Tend to be used when the findings of previous research suggest a particular outcome
• What is a non-directional hypothesis

  - does not state the direction of the relationship between the IV and the DV

  
  

  e.g. There is a difference in the DV between IV condition 1 and IV condition 2
• When do we tend to use a non-directional hypothesis


  Tend to be used when there is no previous research carried out which related to the studies aim or the research is contradictory
• What is a null hypothesis

  states that the result of an experiment will not show a difference or a relationship between two variables.
• What are the 5 types of sampling methods

  1. Opportunity sampling

  2. Random sampling

  3. Stratified sampling

  4. Systematic sampling

  5. Volunteer sampling