Chapter 4: Defining and Measuring Variables LEARNING OUTCOMES. After studying this chapter students should be able to: Distinguish between qualitative and quantitative, discrete and continuous, and independent and dependent variables. Describe what constructs, mediator variables, and moderator variables are. Explain why it is important for scientists to be explicit about how they conceptually define their variables. Discuss what it means to operationally define a variable, and describe some examples of how a construct can be operationally defined. Describe the basic characteristics of nominal, ordinal, interval, and ratio scales. Provide examples of measures that reflect four measurement scales. Describe what is meant by the accuracy and reliability of a measure. Explain how test–retest reliability and internal-consistency reliability can be determined. Explain how validity differs from reliability, and describe the various types of validity. KEYWORDS Accuracy Operational definition Construct Ordinal scale Construct validity Qualitative variable Content validity Quantitative variable Continuous variable Random measurement Criterion validity Ratio scale Dependent variable Reliability Discrete variable Scales of measurement Face validity Situational variable Independent variable Subject variable Internal-consistency reliability Systematic (bias) Interval Test–retest reliability Measurement Validity Mediator variable Variable Moderator variable Nominal scale
Chapter 4: Defining and Measuring Variables LEARNING OUTCOMES. After studying this chapter students should be able to: Distinguish between qualitative and quantitative, discrete and continuous, and independent and dependent variables. Describe what constructs, mediator variables, and moderator variables are. Explain why it is important for scientists to be explicit about how they conceptually define their variables. Discuss what it means to operationally define a variable, and describe some examples of how a construct can be operationally defined. Describe the basic characteristics of nominal, ordinal, interval, and ratio scales. Provide examples of measures that reflect four measurement scales. Describe what is meant by the accuracy and reliability of a measure. Explain how test–retest reliability and internal-consistency reliability can be determined. Explain how validity differs from reliability, and describe the various types of validity. KEYWORDS Accuracy Operational definition Construct Construct validity Content validity Continuous variable Criterion validity Dependent variable Discrete variable Face validity Independent variable Internal-consistency reliability Interval Measurement Mediator variable Ordinal scale Qualitative variable Quantitative variable Random measurement Ratio scale Reliability Scales of measurement Situational variable Subject variable Systematic (bias) Test–retest reliability Validity Variable Moderator variable Nominal scale
Passer_ir_ch04.docx