Psychologie Hoofdstuk 3: Variabelen

Chapter 3: Defining and Measuring Variables

• The research process involves finding an unanswered question, forming a hypothesis, developing an empirical study to support or refute the hypothesis, and defining how each variable will be measured.
• Theories contain hypothetical mechanisms and intangible elements to explain and predict behaviour.
• Hypothetical constructs are attributes or mechanisms that help explain and predict behaviour.
• External stimuli can influence constructs, and constructs can influence external behaviour.

Operational Definitions

• Operational definitions are procedures for indirectly measuring and defining variables that cannot be directly observed.
• They specify a measurement procedure, using observable behaviour as a definition and measurement of the hypothetical construct.
• Operational definitions can also be used to define variables to be manipulated.

Limitations of Operational Definitions

• Operational definitions are not the same as the construct itself.
• Concerns exist about the quality of operational definitions and the measurements they produce.
• There is no one-to-one relationship between the variable being measured and the actual measurements produced by the operational definition. Two common problems are easy to identify in operational definitions.

Validity and Reliability of Measurement

• Validity and reliability are two criteria for evaluating the quality of a measurement procedure.
• Consistency of a relationship is established by demonstrating the consistency of measurements between two different measurements. This can be displayed in a scatter plot.
• Reliability or validity of measurements is established through consistent positive or negative correlations, depending on the definition and measurement of the variables.
• Correlations are commonly used to determine validity and reliability.

Criteria for Validity of Measurement

• To establish validity demonstrates the measurement procedure is actually measuring what it claims to be measuring.
• Face validity concerns the appearance of a measurement procedure, its face value. Subjective judgment makes a more difficult procedure of quantifying this aspect.
• Concurrent validity establishes the validity of a new measurement technique by demonstrating a relationship to another well-established procedure for measuring the same variable. Consistency between two different measurements are established.
• Construct validity means that past research has demonstrated how a specific variable behaves. If you can demonstrate that a variable behaves in the same way as its measurement, this demonstrates construct validity.
• Predictive validity means that measurement of a construct accurately predicts behaviour.
• Divergent validity involves creating two different methods for measuring the same construct and then showing that the two methods produce strongly related scores. Goal is to prove a distinctive construct from one measure against another.

Criteria for Reliability of Measurement

• A reliable measurement procedure produces consistent results when repeatedly used to measure the same individual under the same conditions.
• It is the stability or consistency of the measurements produced by a specific measurement procedure.
• Reliability analysis is based on the assumption that the variable being measured is stable or constant.

Types and Measures of Reliability

• Successive measurements (test-retest reliability): comparing scores obtained from two successive measurements of the same individual.
• Simultaneous measurements (inter-rater reliability): degree of agreement between two observers who simultaneously record measurements of behaviour.
• Internal consistency (split-half reliability): obtained by splitting questionnaire/test items in half, calculating separate scores for each half, and calculating the degree of consistency between the two scores for participants.

Relationship between Reliability and Validity

• Reliability is a prerequisite for validity. A measurement procedure cannot be valid unless it is reliable. However, a measure can be reliable without being valid.
• Possible to define the accuracy of a measurement process with established standard measurement units.

Scales of Measurement

• Nominal scale: categories with different names, but not related.
• Ordinal scale: categories organized in an ordered series (ranks). It establishes whether two individuals are different and the direction of difference.
• Interval scale: categories are the same size, with equal intervals between points.
• Ratio scale: has a true zero point, allowing for comparisons in terms of ratios.

Modalities of Measurement

• Self-report measures: direct questions to participants.
• Physiological measures: brain-imaging techniques.
• Behavioural measures: observing overt behaviour.

Other Aspects of Measurement

• Multiple measures: using two or more different procedures to measure the same variable.
• Sensitivity & Range effects: Measurement may also have issues with range sensitivity of the procedure. High values (ceiling effects) or low values (floor effects) can limit its usefulness.

Artefacts in Experiments

• Experimenter bias: occurs when measurements are influenced by the experimenter's expectations or personal beliefs.

• Paralinguistic and Kinaesthetic cues: Body language, tone of voice, posture can influence participants' behaviour, possibly resulting in biased results.

• Participant reactivity: participants modify their behaviour in response to the knowledge that they're participating in a research study.

• Good subject role: Participants attempt to produce responses that support the investigator's hypothesis.

• Negativistic subject role: Participants attempt to act contrary to the investigator's hypothesis.

• Apprehensive subject role: Participants are concerned that their performance will be evaluated.

Measurement Across Cultures

• Translation of measures across cultures can be problematic; languages vary regarding the number of color words.
• Forward-backward translation procedures can improve on this issue.