CAS 301 Study Guide
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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
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
- 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)
- Participant's reaction to the situation
- Dependent variable (when there is an independent variable) or criterion variable (where there is a predictor variable)
- Individual differences about the participant
- Predictor Variables
What is a conceptual definition of a variable?
- The dictionary definition
- Explanation or description of a variable
What is an operational definition?
- How you will measure the variable
- Definition in your own words
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
What is the difference between the direction and strength of a correlation coefficient?
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
Negative Linear Relationships
- One Variable increases and the other variable decreases
- Example: constant discipline increase, the negative behavioral problems decrease
No Relationship Linear Relationships
- = zero
- There is no systematic relation between the variables
- 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
- No numerical values
- Basic Scales
- Named Categories
- Anything you cannot put in order
- Example - gender, ethnicity, any yes/no questions
- 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
- 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
What is a Likert Scale?
- Ordered rating categories
List the major types of measures
- Direct Test
What is error in a measure?
- Source of error - Operational definition isn't consistent: reliability
- Operational definition doesn't match: Validity
What is reliability?
- Consistency or stability of a measure of behavior
- The degree to which a measure is consistent
- 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.
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.
- 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.
- A indicator of internal consistency reliability assessed by examining the average correlation of each item (question) in a measure with every other question
What is validity?
- The Truth and accurate representation of information about your study and measures.
- The degree to which a measurement device appears to accurately measure a variable
- look at the measure to see if it has "face" value
- 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
- 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
- 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
- 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.
What is external Validity?
The degree to which the results of an experiment may be generalized.
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