MEASUREMENT OF VARIABLES: OPERATIONAL DEFINITION AND SCALES CHAPTER 8

HOW VARIABLES ARE MEASURED? Two types of variables: Variable that lends itself to objective and precise measurement Variable that doesn’t lend itself to accurate measurement because of its subjective nature. Abstract notions  observable characteristic behavior  measurable in a tangible way  called operationalizing the concepts Operational definition is a statement of the specific dimensions and elements through which a concept will become measurable

OPERATIONAL DEFINITION: DIMENSIONS AND ELEMENTS

OPERATIONAL DEFINITION: DIMENSIONS AND ELEMENTS

SCALES very low very high Nominal Scales: splits data into groups, e.g., men, women Ordinal Scales: ranks data in some order, e.g., exercising for 20 minutes is good, for 30 minutes is better, for 40 minutes is best Interval Scales: sets data on a continuum, e.g. 1 2 3 4 5 very low very high Ratio Scales: starts with absolute zero and indicates proportion, e.g. 0 5 10 ten is twice as big as five

MEASUREMENT: SCALING, RELIABILITY, VALIDITY CHAPTER 9

SCALING TECHNIQUES: 1. Rating Scales Dichotomous Scales  yes or no answer Category Scales  uses multiple items to elicit a single response Likert Scales  to examine how strongly subjects agree or disagree with statement on a 5-point scale Semantic Differential Scales  several bipolar attributes are identified at the extremes of the scale Numerical Scales  similar with Semantic Differential Scales with number on 5 or 7 point scale are provided

SCALING TECHNIQUES: 1. Rating Scales…con’t Itemized Rating Scales  a 5 or 7 point scale with anchors is provided for each item and the respondent state the appropriate number on the side of each item Fixed or Constant Sum Rating Scales  the respondents are asked to distribute a given number of points across various items, the sum is constant Stapel Scales  measure both direction and intensity of the attitude toward the item under study Graphic Rating Scales  placing a mark at the appropriate point on the line

SCALING TECHNIQUES 2. Ranking Scales Paired Comparisons  used when, among small number of objects, respondents are asked to choose between two objects at a time. Forced Choice  enables respondents to rank objects relative to one another, among alternatives provided. Comparative Scales provides a benchmark or a point of reference to assess attitude toward the current object, event, or situation under study.

GOODNESS OF MEASURES Stability Internal Consistency Validity Test-retest reliability Parallel-form reliability Internal Consistency Split-half reliability Interitem consistency reliability Validity Content Validity Face validity Criterion-Related Validity Concurrent validity Predictive validity Construct Validity