XP- 4- Defining and Measuring Variables

Theory

set of statements about the mechanisms underlying a particular behavior.

Theory

help organize and unify different observations of the behavior and its relationship with other variables

Theory

a good - generates predictions about behavior

Constructs

hypothetical attributes or mechanisms that help explain and predict behavior in theory

1. Manipulation of antecedent conditions

2. Antecedent condition must have two different conditions

3. Measure the response of behavior of subjects as a result of the treatment condition

A psychology experiment has three main features:

Independent variable

the antecedent condition an experimenter intentionally manipulates

Levels

the values of the IV created by the experimenter

2

an experiment requires atleast - levels

Confounded

An experiment is - when when the value of an extraneous variable systematically changes along with the independent variable

Dependent variable

the outcome measure the experimenter uses to assess the change in behavior produced by the independent variable.

Operational definition

the outcome measure the experimenter uses to assess the change in behavior produced by the independent variable.

Operational definition

procedure for indirectly measuring and defining a variable that cannot be observed or measured directly

Operational definition

specifies a measurement procedure (a set of operations) for measuring an external, observable behavior and uses the resulting measurements as a definition and a measurement of the hypothetical construct.

Experimental operational definition

specifies the exact procedure for creating values of the independent variable.

Measured operational definition

specifies the exact procedure for measuring the dependent variable.

Nominal scale

assigns items to two or more distinct categories that can be named using a shared feature, but does not measure their magnitude.

Ordinal scale

measures the magnitude of the dependent variable using ranks, but does not assign precise values.

Interval scale

measure the magnitude of the dependent variable using equal intervals between values with no absolute zero point.

Ratio scale

measures the magnitude of the dependent variable using equal intervals between values and an absolute zero.

Positive relationship

the two measurements change together in the same direction

Negative relationship

two measurements change in opposite directions

Reliability

refers to the consistency of experimental operational definitions and measured operational definitions.

Reliability

stability or consistency of the measurement

Interrater reliability

the degree to which observers agree in the measurement of the behavior.

Test-retest reliability

means the degree to which a person's scores are consistent across two or more administrations of a measurement procedure.

Test-retest reliability

The reliability estimate obtained by comparing the scores obtained from two successive measurements is commonly called

Parallel-forms reliability

When different versions of the instrument are used for the test and the retest, the reliability measure is often called

Inter-rater reliability

is the degree to which observers agree in the measurement of the behavior.

Interitem reliability

measures the degree to which different parts of an instrument (questionnaire or test) that are designed to measure the same variable achieve consistent results.

Split-half reliability

obtained by splitting the items on a questionnaire or test in half, computing a separate score for each half, and then calculating the degree of consistency between the two scores for a group of participants.

Validity

means the operational definition accurately manipulates the independent variable or measures the dependent variable.

Validity

the degree to which the measurement process measures the variable that it claims to measure.

Face validity

is the degree to which the validity of a manipulation or measurement technique is self-evident.

Face validity

least stringent form of validity

Content validity

means how accurately a measurement procedure samples the content of the dependent variable.

Predictive validity

means how accurately a measurement procedure predicts future performance.

Predictive validity

demonstrated when scores obtained from a measure accurately predict behavior according to a theory

Construct validity

how accurately an operational definition represents a construct.

Construct validity

reqires that the scores obtained from a measurement procedure behave exactly the same as the variable itself.

Concurrent validity

demonstrated when scores obtained from a new measure are directly related to scores obtained from an established measure of the same variable.

Convergent validity

demonstrated by a strong relationship between the scores obtained from two (or more) different methods of measuring the same construct.

Divergent validity

demonstrated by showing little or no relationship between the measurements of two different constructs.

Internal validity

the degrees to which changes in the dependent variable across treatment conditions were due to the independent variable.

Internal validity

establishes a cause-and-effect relationship between the independent and dependent variables.

Self-report measure

probably the most direct way to assess a construct.

Physiological measures

involve brain-imaging techniques such as positron emission tomography (PET) scanning and magnetic resonance imaging (MRI)

Behavioral measures

provide researchers with a vast number of options, making it possible to select the behaviors that seem to be best for defining and measuring the ­ construct

Multiple-measure technique

One method of obtaining a more complete measure of a construct is to use two (or more) different procedures to measure the same variab

Range effect

the measurement procedure is insensitive to changes that may occur in one direction. In general, this type of sensitivity problem is called a -

Ceiling effect

clustering of scores at the high end of a measurement scale, allowing little or no possibility of increases in value

Floor effect

is the clustering of scores at the low end of a measurement scale, allowing little or no possibility of decreases in value.

Artifact

nonnatural feature accidentally introduced into something being observed.

Artifact

external factor that may influence or distort the measurements

Experimenter bias

occurs when the measurements obtained in a study are influenced by the experimenter’s expectations or personal beliefs regarding the outcome of the study.

Single-blind

A research study is - if the researcher does not know the predicted outcome.

Double-blind

A research study is - if both the researcher and the participants are unaware of the predicted outcome

Demand characteristics

refer to any of the potential cues or features of a study that (1) suggest to the participants what the purpose and hypothesis is and (2) influence the participants to respond or behave in a certain way.

Reactivity

occurs when participants modify their natural behavior in response to the fact that they are participating in a research study or the knowledge that they are being measured.

Good subject role

These participants have identified the hypothesis of the study and are trying to produce responses that support the investigator’s hypothesis.

Negativistic subject role

These participants have identified the hypothesis of the study and are trying to act contrary to the investigator’s hypothesis

Apprehensive subject role

These participants are overly concerned that their performance in the study will be used to evaluate their abilities or personal characteristic

Faithful subject role

These participants attempt to follow instructions to the letter and avoid acting on any suspicions they have about the purpose of the study.

laboratory

Reactivity is especially a problem in studies conducted in a -, where participants are fully aware that they are participants in a study.

Laboratory

is any setting that is obviously devoted to the discipline of ­ science.

It can be any room or any space that the subject or participant perceives as artificial.

Field

place that the participant or subject perceives as a natural environment