Research methods

• Lab experiments are defined by the high amount of control the researcher has over all the variables in the study; the experimenter will control environmental factors like noise and temp as well as the experience each ppt has by using standardised procedures
• In lab experiments, the IV is manipulated by researcher between each condition; any change in the DV will be measured whilst all other factors that can affect the DV are kept consistent between the two conditions
• positives of a lab experiment?

  + researchers can be confident in establishing a cause and effect relationship between changes of IV and observed differences in DV

  + high internal validity; observed change in DV is due to change in IV

  + easily replicated due to standardised procedures
• limitations of lab experiments?

  — lack ecological validity as cant be applied to real world situations

  — don’t reflect kind of tasks performed in real world situations; lacks mundane realism therefore lowers external validity

  — ppts aware they are in a study therefore may change their behaviour due to demand characteristics; change behaviour to match the aim
• field experiments are defined by conducting the experiment in naturalistic settings; this change in location is an attempt to avoid the artificial nature of lab studies; locations can include anywhere that the ppts would be expected to act naturally
• in a field experiment, the iV is still changed by the researcher between the two conditions and the researcher then measures the difference in the DV
• strengths of a field study?

  + ppts should behave more naturally in normal environment; applied to naturalistic settings therefore increasing ecological validity

  +wont show demand characteristics

  + mundane realism; activities carried out often by ppts in day to day life
• limitations of field experiment?

  — lack control over extraneous variables that can influence measurement of dependent variable

  — difficult to randomly assign ppts to separate conditions
• Natural Experiments: The two levels of independent variables have (or will) occurred naturally (in the real world) without the influence of the researcher. The researcher simply records the change in the dependent variable between the two levels of IV.

  Natural experiments can happen whenever an event causes people to form into levels of the independent variable. For example, this could be a literal natural event like a disaster or political decisions that only impact some members of a community.
• in a field experiment The independent variable (IV) is NOT changed by the researcher between the conditions of the experiment. Changes in the dependant variable (DV) are still measured but other possible variables that could change the DV cannot be controlled.
• strengths of natural experiment?

  + Natural experiments allow research in areas that could not happen in controlled experimentation, either due to ethical or cost reasons.

  + High in external validity as natural experiments are an example of real behaviour occurring in the real world free of demand characteristics.
• limitations of natural experiments?


  — As these events have already or will happen regardless of the researcher, they have no influence. This means extraneous variables can't be controlled, so the researcher shouldn't claim they have found a cause and effect relationship.

  — These are often very rare events that can't be replicated exactly to test for reliability
• Quasi-experiments: Participants cannot be randomly assigned between levels of IV.

  Often because the level of IV is an innate characteristic of the participants.

  There is a wide range of characteristics that psychologists would like to study, but these characteristics already exist in the sample, for example, gender, age, income level, educational level, and people with our without a mental health condition.
• in a quasi experiment the Independent variable (IV) already exists in the participants so participants cant be randomised between the conditions of the experiment. The difference in the dependant variable (DV) will be measured while all other possible variables that could change the V are kept constant.
• strengths of a quasi experiement?

  + Quasi-experiments are the only way to experimentally study factors that are pre-existing, characteristics of participants.
• limitations of a quasi experiment?


  — There may be other factors related to the level of IV that cannot be controlled for, these change systematically between the levels of IV and alter the measurement of the dependant variable. These are known as confounding variables.