Experimental methods Flashcards
What is an experiment?
-Manipulation of one or more variables (e.g coffee intake) and determine the effect of this manipulation on another variable
-To test cause-effect relationships between variables
What are the two type of hypothesis?
Alternative
Null
What is the difference between alternative and null hypothesis
Alternative = Treatment leads to an effect
Null = -treatment does not lead to an effect
What is the relationship between the two types of variables
-Manipulating the independent variable changes the outcome of the dependant variable
What do you do when you have more than one independent variable ?
Include them in one experiment = this is better than several experiments testing IV’s independently as its:
- more efficient
- better control of nuisance variables
- results often more representative of behaviour
What do you do when you have more than one dependant variable
Measuring more than one DV is usually more informative as it give more insight
What is a nuisance variable?
An additional factor that affects the dependent variable Nuisance but all levels of the IV are affected equally.
What does a nuisance variable turn into?
A confounding variable
How do you deal with a nuisance variable
- Turn it into a control variable (held constant)
- If it is such a nuisance it can be turned into an IV
What is an experimental group?
Group receiving the important level of the independent variable
What is a control group?
Group that serves as the untreated comparison group
-Serves as a comparison level of the independent variable
Name two advantages of experiments
-Relative strong test casualty (e.g what leads to what)
-Possibility of a variety of manipulative control
Name 4 disadvantages of experiments
- Unnatural setting and tasks
- Reactivity
- Some phenomena cannot be studied under controlled conditions
- Ethical limitations
What is a between subjects design?
Participants take part in separate conditions
What are the two subject designs?
Within
Between
What is a within subjects design?
All participants receive all levels of the independent variable
Give two advantages of using a within subjects design
- Fewer participants required
- Reduces individual differences (less confounding variables)
Give two disadvantages of using a within subjects design
-Carryover effects
-Order effects
What are Quasi experiments?
- When one or more independent variables are selected but not manipulated
- Looking at information that is there already
Give one advantage and one disadvantage of Quasi experiments
A = Examination of variables that would be unethical to manipulate (e.g. effects of growing up in a poor area)
D = No strong conclusions about cause and effect possible
What are the 3 sampling types?
Random sample
Stratified sample
Quota sample
What is random sampling?
everyone has an equal chance of being selected
-Can be practically difficult
What is stratified sampling?
Random selection of each subgroup of the population
What is Quota sampling?
Representative sample that meets quota/ targets
-sample involving individuals that represent a particular population.
