Measurement of variables

1. MEASUREMENT OF
VARIABLES:
OPERATIONAL
DEFINITION AND SCALES
CHAPTER 8

2. 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

3. OPERATIONAL DEFINITION: DIMENSIONS AND ELEMENTS

4. OPERATIONAL DEFINITION: DIMENSIONS AND
ELEMENTS

5. SCALES
1 2 3 4 5
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.
Ratio Scales: starts with absolute zero and indicates
proportion, e.g.
0 5 10 ten is twice as big as five

7. MEASUREMENT:
SCALING,
RELIABILITY,
VALIDITY
CHAPTER 9

8. SCALING TECHNIQUES:
1. Rating Scales
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

9. 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

10. 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 TECHNIQUES
2. Ranking Scales

11. GOODNESS OF MEASURES
Stability
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