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

Nominal Scales: splits data into groups, e.g., men, womenOrdinal Scales: ranks data in some order, e.g., exercising for 20 minutes is good, for 30 minutes is better, for 40 minutes is bestInterval Scales: sets data on a continuum, e.g.1 2 3 4 5very 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, VALIDITYCHAPTER 9

SCALING TECHNIQUES:1. Rating ScalesRating 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

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:1. Rating Scales…con’t

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.

SCALING TECHNIQUES2. Ranking Scales

GOODNESS OF MEASURESStability Test-retest reliability Parallel-form reliability

Internal Consistency Split-half reliability Interitem consistency reliability

ValidityContent Validity Face validity

Criterion-Related Validity Concurrent validity Predictive validity

Construct Validity