Chapter 3 Flashcards
Defining and Measuring Variables
(Hypothetical) constructs
Hypothetical attributes or mechanisms that help explain and predict behavior in a theory.
Theory
A set of statements about the mechanisms underlying a particular behavior. Theories help organize and unify different observations of the behavior and its relationship with other variables. A good theory generates predictions about the behavior.
Operational definition
A procedure for indirectly measuring and defining a variable that cannot be observed or measured directly. An OD specifies a measurement procedure (a set of operations) for measuring an external, observable behavior and uses the resulting measurements as a definition and a measurment of the hypothetical construct.
Validity
The degree to which the measurement process measures the variable it claims to measure.
Face validity
Does the measurement technique look like it measures the variable that it claims to measure? Face validity is based on subjective judgment.
Concurrent validity
When scores obtained from a new measurement technique are directly related to the scores obtained from another, better-established procedure for measuring the same variable.
Predictive validity
When the measurements of a construct accurately predict behavior (according to the theory).
Construct validity
The scores obtained from a measurement procedure behave exactly the same as the variable itself. It is based on many research studies that use the same measurement procedure.
Convergent validity
A strong relationship between scores is obtained by two (or more) different methods of measuring the same constuct.
Divergent validity
Demonstrated by showing little or no relationship between the measurements of two different constructs.
Reliabilty
The stability or consistency of a measurement. If the same individuals are measured under the same conditions, it should produce (nearly) identical results.
Successive measurements: Test-retest reliability
Established by comparing the scores obtained from two successive measurements of the same individuals and calculating a correlation between the two sets of scores.
If alternate forms of the measuring instrument are used for two measurements, it is called parallel-forms reliability.
Simultaneous measurements: Inter-rater reliability
The degree of agreement between two observers who simultaneously record measurements of the behaviors.
Internal consistency: Split-half reliability
Obtained by splitting the items on a questionnaire or test in half, computing a seperate score for each half, and then calculating the degree of consistency between the two scores for a group of participants.
Scale of measurement (definition)
In general terms, measurement is a procedure for classifying individuals into categories. These categories are called SoM.
The scales of measurement (the four types)
The nominal scale, the ordinal scale, the interval scale and the ratio scale.
The nominal scale
The categories represent qualitative differences in the variable measured (such as college major, race, occupation etc.). This scale allows us to determine whether two individuals are the same or different, but they do not permit any quantative comparison.
The ordinal scale
Often, an ordinal scale consists of a series of ranks (1st, 2nd, 3rd or XS, S, M etc.). The categories form an ordened sequence which means there is a directional relationship between the categories. Ordinal measurements do not allow us to determine the magnitude of difference.
The interval scale
The categories are organized sequentially, all categories are the same size (time in seconds, weight in pounds, temperature etc.) Since the categories are the same size, it is possible to determine the distance between two points on the scale.
The interval scale has an arbitrary zero point. The value of 0 is assigned to a particular location on the scale. The value 0 does not mean there is a total absence of the variable being measured (e.g. 0 degrees Celcius).
The ratio scale
The categories are organized sequentially, all categories are the same size (time in seconds, weight in pounds, temperature etc.) Since the categories are the same size, it is possible to determine the distance between two points on the scale.
The ratio scale is characterized by zero point that is not an arbitrary location. Instead, the value 0 on a ratio scale is a meaningful point representing none, a complete absence.
Because of this, we can measure the distance from a point from zero. This makes it possible to compare measurements in terms of ratios.
Three modalities (types) of measurement
- self-report
- physiological
- behavioral
Ceiling effect
The clustering of scores at the high end of a measurement scale, allowing little to no possibility of increases in value.
Floor effect
The clustering of scores on the low end of a measurement scale, allowing little to no possibility of decreases in value.
Artifact
A nonnatural feature accidentally introduced into something being observed, which may influence or distort measurement.
