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What is a variable? What is a level or value of a variable?
Variable - any event, situation, behavior, or individual characteristic that varies - that is, has at least two variables
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What is a level of a variable? or value of a variable?
- Specific instances of the variable
- May be quantitative/numerical
- Values, a number with a variable
- May be instances of a category
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Situational Variable
- Describe characteristics of a situation or environment
- May pre-exist or be manipulated by researcher - previous experiment
- to study things that are all ready there
- Predictor Variable (when pre-exists) or independent variable (when manipulated by the researcher)
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Response Varaible
- Participant's reaction to the situation
- Behavior/Outcome
- Dependent variable (when there is an independent variable) or criterion variable (where there is a predictor variable)
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Participant/Subject Variables
- Individual differences about the participant
- Pre-existing
- Predictor Variables
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What is a conceptual definition of a variable?
- The dictionary definition
- Explanation or description of a variable
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What is an operational definition?
- How you will measure the variable
- Definition in your own words
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What is a linear relationship between variables? How is a linear relationship measured?
- Linear Relationships - relationship measured with correlation coefficient and direction and strength
- Correlation Coefficient - Relationship between two variables
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What is the difference between the direction and strength of a correlation coefficient?
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Positive Linear Relationship
- One variable increases, the other variable also increases
- A one slope = a perfect slope
- Example: hot weather/crime - the higher the temp goes the higher the crime rate goes
- Range: 0 to 1.00
- Correlation Coefficient -
- -1.00 to 1.00
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Negative Linear Relationships
- One Variable increases and the other variable decreases
- Example: constant discipline increase, the negative behavioral problems decrease
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No Relationship Linear Relationships
- = zero
- There is no systematic relation between the variables
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Curvilinear Relationships
- Cannot measure with a simple correlation coefficient
- Increases in one variable are sometimes associated with an increase in the other variable and sometimes associated with a decrease in the other variable
- Increase/Increase
- Decrease/Decrease
- Increase/Decrease
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Nominal Scales
- No numerical values
- Categories
- Basic Scales
- Named Categories
- Anything you cannot put in order
- Example - gender, ethnicity, any yes/no questions
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Ordinal Scales
- Ordinal Scales - A scale of measurement in which the measurement categories form a rank order along a continuum
- Ranked from first to last
- Difference between the categories is not necessarily the same
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Interval Scales
- Interval Scales - A scale of measurement in which the intervals between numbers on the scale are all equal in size
- Difference between numbers on scale is meaningful
- Interval are EQUAL IN SIZE
- No true zero
- Example - Temperature
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What is a Likert Scale?
- Ordinal
- Ordered rating categories
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List the major types of measures
- Questionnaires/Surveys
- Interviews
- Observations
- Direct Test
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What is error in a measure?
- Source of error - Operational definition isn't consistent: reliability
- Operational definition doesn't match: Validity
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What is reliability?
- Consistency or stability of a measure of behavior
- The degree to which a measure is consistent
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Test-Retest Relaibility
- A reliability coefficient determined by the correlation between scores on a measure given at one time with scores on the same measure given at a later time.
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Internal Consistency Reliability
- Reliability assessed with data collected at one point in time with multiple measures of a psychological construct. - A measure is reliable when the multiple measures provide similar results.
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Split-half Reliability
- A reliability coefficient determined by the correlation between scores on half of the items on a measure with scores on the other half of the measure.
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Cronbach's Alpha
- A indicator of internal consistency reliability assessed by examining the average correlation of each item (question) in a measure with every other question
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What is validity?
- The Truth and accurate representation of information about your study and measures.
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Face Validity
- The degree to which a measurement device appears to accurately measure a variable
- look at the measure to see if it has "face" value
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Predicitve Validity
- Related to other things that it should be related to in the future
- Measure something today and compare it to something in the future
- Example - aggression in 10 year olds and the crime rate in the future
- The construct validity of a measure is assessed by examining the ability of the measure to predict a future behavior
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Concurrent Validity
- Related to other things that it should be related to at the same time
- Done at the same time
- Example - SAT scores senior year should be related to current GPA
- The construct validity of a measure is assessed by examining whether groups of people differer on the measure in expected ways
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Convergent Validity
- Similar to other measures of the same thing
- Multiple measures of the same thing
- Example - teacher survey of children and observations of the children - they should be the same
- The Construct validity of a measure is assessed by examining the extent to which scores on the measure are related to scores on other measures of the same construct or similar constructs
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Discriminant Validity
- Different from measures of other things
- Low relationships between the 2 measures
- Personality scores should not be related to ones reading ability, therefore, no relationship
- The Construct validity of a measure is assessed by examining the extent to which scores on the measure are not related to scores on conceptually unrelated measures.
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What is external Validity?
The degree to which the results of an experiment may be generalized.
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