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What is a variable
Anything we measure, or can change, be held constant etc. It is an event situation, behavior, or individual characteristic that varies.
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How many levels should a variable have?
two
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What kind of values may a variable have?
Numeric or qualitative
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What is a operational definition for a variable?
- A set of procedures to measure or manipulate it
- -it helps with communicating meaning to others
- -Requires definition in concrete terms
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What is construct validity
Am I measuring what I say I'm measuring? Does operational definition reflect meaning of variable?
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What is a positive linear relationship
Increases in one variable are accompanied by increases in another variable (diagonal line going up)
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Negative linear relationship
Increases in one relationship and decreases in another
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Curvilinear relationship
- Increases in one variable are accompanied by systematic increases and decreases in another variable
- -direction of relationship changes
- -May be U-shaped or inverted U-shaped.
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No relationship
No association between variables (flat line)
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What is a correlation coeficient
The number between 0-1 that accompanies the negative or positive symbol.
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What does a correlation coefficient do?
- -Indicates how strongly variables are related (closer to one, stronger relationship is)
- -Allows prediction of changes in one variable from changes in another
- -Helps explain random variability
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Nonexperimental mothods
Relationships are studied by making observations or measures of the variable of interest.
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What are some nonexperimental methods?
- -Self-report descriptions of behavior
- -Direct observation
- -Recording physiological
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- -examining public records
- -variables observed as if they occurred naturally and relationship established if vary together.
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What constitutes a non-experimental method?
-No variable is manipulated-all measured
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What are some problems with non-experimental methods?
- -Not good when trying to determine cause and effect
- -difficult to determine direction of relationship
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Experimental methods
Experimenter manipulates a variable and observes the effect on a second variable
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What do you do with the variables in an experimental method?
Manipulate one, measure the other-allows for determination of direction of cause and effect
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What does the experimental method attempt to do?
Control potential extraneous variables or confounding variables
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In an experimental method, everything is held constant except for what?
manipulated variable
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What kind of procedures are used in experimental method?
Randomization
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What is experimental control?
- All extraneous variables are held constant
- -treat all participants from all groups identically, except for manipulated variable.
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What does experimental control eliminate
Confounding variables
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What does randomization do?
Ensures that an extraneous variable is just as likely to affect one experimental group as it is the other groups in the experiment
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Random assignment
for between subjects design (each participant participates in one thing)-randomly assign to groups (random number draw).
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Counterbalancing
within subject design (everybody goes through each condition) but the condition order is randomized for each person with a break inbetween.
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