Chapter 8 Flashcards
How are all other variables controlled in experimental method
Experiment control
Randomization
Confounding variable
Variable that varies along with the independent variable
It occurs when efffects of independent variable and an uncontrolled variable are intertwined so you cannot determine which of the variables is responsible for the observed effect
When the results of an experiment can confidently be attributed to the effect of the independent variable, the experiment is said to have…
Internal validity
How does one achieve good internal validity?
Researcher myst design and conduct the experiment so that only the independent variable can be the cause of the results
A researcher using a Posttest only design must..:
Obtain two equivalent groups of participants
Introduce the independent variable
Measure the effect of the independent variable on the dependent variable
Why must pisttest only design use two EQUIVALENT groups?
To eliminate any selectional differences
Selection differences
Differences in the type of subjects who make up each group in an experimental design
This situation occurs when participants elect which group they are to be assigned to
Difference between pretext only design and pretext post test
In protest post test, a pretext is given before the experimental manipulation is introduced
Why in pretext posttest, is pretext given before manipulation
Makes it possible to ascertain that groups were infact equivalent from the beginning
It is not always needed in a large sample of participants that has random assignment
drop out factor is caused
Attrition or mortality
Fallbacks of a pretest
It can sensitize participants to what you are studying, enabling them to figure out what you are studying and why
Solomon design
Half of participants receive only the post test and half receive both the pre test and the post test
Independent group design (also known as between subjects design)
When participants are randomly assigned to the various conditions so that the each participated in only ONE group
Comparisons are made between different groups of participants
Repeated measure design
Participants receive all conditions
When each participant is measured after receiving each level of the independent variable.
(Also called within subject design)
Random assignment
Decision to assign an individual to a particular condition is completely random and beyond the control of the researcher
Advantages of repeated measure design
Fewer research participants are needed because each individual participated in all conditions
They are extremely sensitive to finding statistical significant differences between group.
Two ways to assign participants to a group
Indenpendent group design (only participated in one )
repeated measure design (participated in all)
Advantages of pretest post test
Ensure consistency (aka experimental control)
Can help with subject selection criteria
Can determine change between pretest and post test
Can determine if attrition (aka mortality) affected results
Pre test post test disadvantages
Demand characteristics (like filler ideas)
Time, money, effort, etc
How to ensure equivalency between two groups
Random assignment
Repeated measures design (ak within subjects) advantages
Fewer Ss needegreater statistical “sensitivity” by deducting random error
Disadvantages of experimental design
Order effects
Counterbalancing
Threats to internal validity highlighted by quasi experiment designs
History Maturation Testing Instrument decay Progression toward the mean Attrition or drop out
Order effect
The order of presenting the treatments effect the dependent variable
