CAS 301 Study Guide
Card Set Information
CAS 301 Study Guide
Chapters Variables Measurement
Chapters 4 and 5
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
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
: hot weather/crime - the higher the temp goes the higher the crime rate goes
: 0 to 1.00
Correlation Coefficient -
-1.00 to 1.00
Negative Linear Relationships
One Variable increases and the other variable decreases
: constant discipline increase, the negative behavioral problems decrease
No Relationship Linear Relationships
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
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
What is error in a measure?
Source of error - Operational definition isn't consistent
Operational definition doesn't match
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.