Psychological Investigations : The experimental method
- Created by: Thomas J Betambeau
- Created on: 21-05-13 15:45
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- The experimental method
- Key features
- Theory
- Test
- Control
- Replication
- In order for support for a theory to be retested it is vital that any experiment can be replicated by others
- Has to be under controlled conditions, to make sure you are finding results due to only an identified variable
- Replication
- You have to make sure that the variable you are manipulating has a measurable effect on the other variable
- Control
- You need a hypothesis to try and prove/disprove
- Hypothesis
- Null hypothesis
- There will be no significant difference on the performance on a memory test between participants who are tested at 10am and 10pm
- Alternate hypothesis
- Two tailed
- There will be a significant difference in performance between participants tested in the morning and in the evening
- One tailed
- Participants will perform better in the morning than in the evening
- Two tailed
- A hypothesis is a testable, predictive statement
- Null hypothesis
- Hypothesis
- Test
- Theory
- Designing an experiment
- Come up with a hypothesis
- Design an experiment to test the hypothesis
- Manipulate one factor (IV) that you have identified in the hypothesis to cause a particular effect
- Measure the effect of this manipulation. The factor that is measured is the DV.
- Analyse the results from other conditions and compare the mean results. If there is a difference this supports the hypothesis
- Measure the effect of this manipulation. The factor that is measured is the DV.
- Manipulate one factor (IV) that you have identified in the hypothesis to cause a particular effect
- Design an experiment to test the hypothesis
- Come up with a hypothesis
- In an experiment there are IVs and DVs
- In a true experiment the researcher manipulates the IV and in this way creates the different conditions of the experiment
- The DV is whatever the researcher has chosen to measure as a consequence of the manipulation of the IV.
- Advantages and disadvantages
- Experiments are often low in ecological validity as generaly they are controlled situations removed from real life
- Enables you to test hypotheses.
- Easily replicated due to standardised procedures
- Allows researcher to control extraneous variables therefore improving reliability
- Difficult to orgaise and is not generalisableas sample sizes are usually small
- Participating in experiments may cause anxiety or stress in participants
- There are 3 main experimental designs
- Independent measures
- Participants are randomly allocated to groups and each group is tested in one condition
- Group A in condition A. Group B in condition B.
- E.g. Loftus and Palmer (1974)
- Group A in condition A. Group B in condition B.
- No order effects
- Not possible to control participant variables
- Participants are randomly allocated to groups and each group is tested in one condition
- Repeated measures
- The same participants are tested in two or more conditions. The mean is calculated and if a difference is found, this supports the experimental hypothesis
- Group A in condition A. Group A in condition B.
- Potential order effects
- The same participants are tested in two or more conditions. The mean is calculated and if a difference is found, this supports the experimental hypothesis
- Matched participants
- Participants are divided into groups on the basis of matching one or more criteria such as age, gender etc.
- E.g. Bandura and Ross (1961)
- Extraneous variables are well controlled
- Its impossible to control extraneous variables so in practise normally they are only matched on one or two vriables
- Participants are divided into groups on the basis of matching one or more criteria such as age, gender etc.
- Independent measures
- Key features
- Other variables are controlled
- Measure the effect of this manipulation. The factor that is measured is the DV.
- Analyse the results from other conditions and compare the mean results. If there is a difference this supports the hypothesis
- Measure the effect of this manipulation. The factor that is measured is the DV.
- Removes participant variables
- Repeated measures
- The same participants are tested in two or more conditions. The mean is calculated and if a difference is found, this supports the experimental hypothesis
- Group A in condition A. Group A in condition B.
- Potential order effects
- The same participants are tested in two or more conditions. The mean is calculated and if a difference is found, this supports the experimental hypothesis
- Repeated measures
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