Experiments Flashcards
What are the three types of experiment?
- Laboratory
- Field
- Quasi (Natural)
What is a laboratory experiment?
The IV is manipulated by the researcher and the experiment is carried out in a lab or other contrived setting (controlled)
What is a field experiment?T
The IV is manipulated by the researcher but the experiment is carried out using the participants normal surroundings
What’s a Quasi experiment?
A natural experiment where the IV occurs naturally and cannot by manipulated by the researcher (eg. sun)
Advantages of laboratory experiment
- Tighter control of variables
- Easier to comment on cause and effect as setting is controlled
- Relatively easy to replicate
Disadvantages of laboratory experiment?
- Demand characteristics - participants are aware of experiment so may change/alter their behaviour
- Artificial environment - has low ecological validity so its difficult to generalise to other situations
- Experimenter effects - bias when expectations affect behaviour
Advantages of field experiment
- Less artificial as its set in the real world situations (more true to life - ecological validity)
- Valid as people are unaware of experimental conditions and are in their natural environment so act genuinely
Disadvantages of field experiment
- Less control over extraneous variables
- Ethical problems; don’t usually gain informed consent of those involved or they’d give away the aim of the study
Advantages of quasi experiments?
- Useful when its unethical to manipulate the IV
- Studies the ‘real effect’ so there is increase realism and ecological validity
Disadvantages of quasi experiments/
- Difficult to get participants
- Expensive/Costly and takes time because you have to wait for IV to occur
- Confounding experiment variables are more likely so less reliable
What are the three experimental designs?
Repeated measures design
Independent measures design
matched participant design
What is a repeated measures design?
involves the use of the same people in each experimental condition
What is an independent measures design ?
Involves using different people in each condition
What is a matched participant design?
Involves the use of different people in each experimental condition but an attempt is made to make the participants as similar as possible on certain key variables
What is a laboratory experiment?
The IV is manipulated by the experimental and is carried out in a lab or contrived/controlled setting
What is a field experiment?
The IV is manipulated by the researcher but it is carried out in the participants normal surroundings/environment
What is a Quasi experiment?
A natural experiment where the IV is naturally occurring (not manipulated by the researcher
What are the advantages of a laboratory experiment?
- Tighter control of variables
- Easier to comment on cause and effect relationship
- Relatively easy to replicate
What are the disadvantages of a laboratory experiment?
- Demand characteristics - participants are aware of experiment so may change behaviour
- Artificial environment- low ecological validity so difficult to generalise to other situations
- Experimenter effects - bias when expectation affects behaviour
What are the advantages of a field experiment?
- Less artificial - set in the real world situations so it’s more true to life (valid)
- Valid as people are unaware of experimental conditions s and they’re in their usual environment
What are the disadvantages of a field experiment?
- Less control over extraneous variables
- Ethical problems - don’t usually gain informed consent of those involved or they’d give away the aim of the study
What are the advantages of a Quasi experiment?
- Useful when unethical to manipulate the IV
- Studies the ‘real effect’ so there is increased realism and ecological validity
What are the disadvantages of a Quasi experiment?
- Difficult to get participants
- Expensive and requires lots of time and effort because you have to wait for the IV to occur
- Confounding experiment variables are more likely so results are less reliable
What is a repeated measures design?
This involves using the same people in each condition
What is the independent measures design?
This involves using different people in each condition
What is a matched participant design?
This involves using different people in each condition but an attempt is made to make the participants as similar as possible on certain key characteristics
Done by testing individual in key variables and pairing them based on similar scores
What are the advantages of repeated measures design?
- Requires less participants saving time and money
- Participant variables were controlled and will not affect results as the same people are used to
- Half the no. of participants are needed than the other two designs
What are the disadvantages of the repeated measures design?
- Order effects : getting worse due to fatigue/getting better due practice, Can affect the results of the second condition, to reduce order effects have ti create additional test materials with identical difficulty level (hard to achieve)
- Demand Characteristics- participants want to produce the correct reults
What are the advantages of independent measures designs?
- Avoids effects (only take part in one condition)
- Demand characteristics are less likely (can’t guess aim of study as only experienced one condition)
- Can use same task in each condition, controlling for any differences in this as a possible extraneous variables
What are the disadvantages of an independent measures design?
- Participant variables can affect behaviour
- Bigger sample is needed - uses more time and money (twice as many needed for same no. of results as repeated measures design
- Results can be affected by participant variables (inevitable individual differences)
What are the advantages of a matched participant design?
- Avoids order effects (one participant per condition)
- Avoid participant variables
- You get benefits of both other designs: order effects are avoided as you only take part in one condition and participant variables aren’t a problem
What are the disadvantages of a matched participant design.
- Requires a bigger sample which requires time and money
- It’s not practical- almost identical participants is difficult to get and factors like tiredness and motivation affect behaviours
- More complicated as participants need pre-testing on relevant characteristics so matched according
What can extraneous variables become if not controlled?
Confounding variable - obscure effects of IV
What are the two types of extraneous variables ?
Participants variables
Situational variables
How can participant variables be controlled?
Either have same/very similar people on each condition (by using repeated measures/matched participant design)
If using an independent measures design make a point of ALLOCATING PARTICIPANTS TO CONDTIONS ON A RANDOM BASIS so that participant variables are more likely to be evenly spread
How to control situational variables like order effects?
Having different people in each condition will avoid this problem (use independent/matched participant design)
If using a repeated measures design then this should be counter-balanced
- participants are split into two groups which group 1 doing condition A then B and group 2 doing condition B then A
How to control situational (environmental factors) variables?
Impose CONTROLS on the experiment to ensure there are as few differences as possible
How to control situational (demand characteristics ) variables
Do not tell participants the aim of the investigation (single blind)
What is a double blind trial?
When neither the participant or the researcher know the aim of the study
A double blind procedure eliminates the danger of (bias)?
Researcher bias
What is researcher bias?
When the researcher allows their hopes and expectations for what data should look like to affect the data they choose to hold onto
What are the two types of hypothesis?
Alternative (One or Two Tailed)
Null
What does an alternative hypothesis do?
This predicts how the IV WILL affect the DV
What are the two types of alternative hypothesis?
One-Tailed (Directional)
Two-Tailed (Non-directional)