Example of a good experiment
Random assignment to groups
- expt grp --> pre test --> expt treatment --> post test
- control grp --> pre test --> post test
Is yawning contagious?
Random Sampling and Random Assignment
One time of randomization, splitting process will have another randomization To avoid bias
Why we need expt and control grp
Need to ensure similarity btw the personal characteristics of the control and expt grp Is it the IV tht cause the changes in the DV or is it a systematic diff btw the participants in both grps Why we need random ASSGMT
Equal chance to be in the expt grp or control grp helps to reduce systematic effects n diff btw participants Balance participant characteristics
Must say I have TWO groups
Isolating the effects of IV
Expts must Exclude all other explanations to ensure cause n effect relationship n therefore extraneous v. Must be controlled. - situational v.
- participant v. N placebo effect
- experimenter effect
Black teeth and white teeth affect appearance
Testing should be done under
- Same conditions
- Same situations
Control v tht are most likely to affect DV response
Individual diff in personal characteristics among participants tht affect the response in an expt. Solution: random assgmt
What is individual diff?
- means diff characteristic tht we have.
Single Blind Procedure
-Double Blind Effect
Let say Giving two grps different treatment
Because of the experimenters giving to diff treatment, results affected So double blind procedure is the experimenter himself also don't know who he is giving to... He is Expt design advantages
- Elimination or control of extraneous variables
- Manipulate IV to observe effect on DV allows inference of casual relationship. - Replicable
Experiment design disadvantages
- Highly controlled...