Defining and Measuring Variables An Overview of Measurement

Defining and Measuring Variables

An Overview of Measurement • Variables – characteristics or conditions that changes or have for different individuals • In order to study variables, we have to know how to define and measure them • How can you measure the following? ▫ Height, age, time, knowledge, familiarity, intimacy, anger, decisiveness, personality

An Overview of Measurement • There is no one-to-one relationship between the variable and the measurements obtained • There are several options for measuring any particular variable • The selection of a measurement procedure involve decisions that can have consequences for the outcome of the study.

Construct and Operational Definition • Abstract, unobservable, intangible variables are more difficult to measure • This variable are to assumed to exist • It motivation is said to be “low, ” how do we know it is? • Many variable are theoretical entities, they are called “constructs” or “hypothetical constructs”

Construct and Operational Definition • In many theories, constructs can be influenced by stimuli and, in turn, can influence behavior • It is possible for researchers to examine the factors that theoretically influence a construct and study the behaviors that theoretical result from a construct

Construct and Operational Definition • Operational Definitions • While it is impossible to actually measure theoretical construct, it is possible to observe and measure the external factors and the behaviors that are associated theoretically with the construct • The resulting measurement of external factors and behaviors are used as a definition and measurement of the construct – operational definition

Construct and Operational Definition • Using Operational Definitions ▫ When variables are hypothetical constructs, you must use operational definitions to define and measure the variables. ▫ This is not the same with creating your own operational definition. ▫ Consult previous research that describe in detail how the construct is defined and measured in a conventional way

Construct and Operational Definition • Using Operational Definitions ▫ Other measurement procedures are always possible and may provide better way to define and measure the variable.

Validity and Reliability of Measurements • A good method of measurement has to meet two important criteria. • Validity – does the method of measurement really measures what it intends to measure? ▫ Very important especially when operational definition is used to measure a hypothetical construct.

Validity and Reliability of Measurements • Reliability – repeated measurements of the same individual, under the same conditions produce identical or nearly identical values. Measured Score = True score + Error