Types of Experiments, Reliability and Validity Flashcards
What is an experiment?
A research method where the IV is manipulated in order to observe and measure its effect on the operationalised DV.
What are the 4 types of experiments that you need to know of?
~ Laboratory
~ Natural
~ Field
~ Quasi
Laboratory experiments
- Take place in an artificial environment
- High levels of control (all variables are controlled)
- IV created by research - manipulated to measure its effect on the DV.
Strengths of Laboratory experiments:
+ High levels of control: control extraneous variables - more certain that changes in DV are due to IV. Stronger cause and effect relationship between IV and DV - increases validity
+ High levels of control: Overall control of all variables + can make them occur in the exact same way when repeating the experiment. - Establishes a standardised procedure and repeat the exp to see if findings are consistent - increases reliability
Weaknesses of Laboratory experiments:
Artificial setting: ppts in unfamiliar surroundings so their behaviour is unnatural and not reflective of everyday life - findings cannot be applied to everyday life - decreases ecological validity.
- Ppts are generally aware that behaviour is being assessed: ppts may display demand characteristics. - decrease in validity of findings and conclusions drawn.
Demand characteristics:
Behaviours that ppts assume the researcher wants to see.
Field experiment
- Real life environment
- Limited level of control
- IV is still manipulated to observe effects on DV
Strength of field experiments:
+ The exp takes place in a natural setting, so ppts are more likely to display natural behaviours (than in lab exp) - findings and conclusions can be applied to everyday life - higher ecological validity.
Weaknesses of Field experiments:
- Lower levels of control compared to lab exp as the researcher has less of a control on all the variables and cannot make them act the same way when repeating the experiment.
- No cause and effect relationship between IV and DV as cannot be sure that only IV is affecting the DV.
Natural experiment
- The IV occurs naturally and is out of the control of the researcher
- Conducted in a natural real life environment
Strengths of natural experiments:
+ Findings can be applied to everyday life as ppts in familiar surroundings and display natural behaviour reflective of their everyday life - increasing ecological validity.
+ Ppts less likely to display demand characteristics
Weaknesses of natural experiments:
- Lack of control: Lack of control of all variables in the exp - so cannot make them occur in the same way when repeating exp - cannot establish standardised procedure- cannot check for consistency - results unreliable
- Lack of control of variables: extraneous variables may influence ppts behaviour. - C+E relationship between IV and DV is weakened as we cannot be certain that IV is the only thing affecting the DV. ++ Random allocation cannot take place as no control over which condition ppts are placed in - decreasing validity.
Quasi experiment
- Types of natural experiments where the researcher has no control over IV.
IV is based on existing differences between ppts (e.g ppts with depression vs without - researcher did not CAUSE depression, it already existed and was a difference between ppts.)
Strength of Quasi experiment
+ Allows researcher to investigate variables that would be unethical to manipulate directly. e.g. trying to induce depression in ppts highly unethical- could cause considerable harm to ppts. By using existing cases of depression or other traits, able to investigate the effect of very important behaviours without causing significant harm.
Weakness of Quasi experiment:
- C+E relationship between IV and DV is weakened bc ppts from diff groups (e.g. depression vs no depression) will have individual differences beyond the trait difference that is being measured by the researcher.
e.g ppts in both groups may differ in terms of background, socio-economic status, IQ, age, etc which would act as extraneous variables.
