1. Measurement Basics
Chapter 13

2. Measurement
“rules for assigning numbers to objects in such a way as to represent quantities of attributes”
- Bennett (1995), pg, 173
SLIDE 13-1

3. Scales of Measurement Ratio Interval Ordinal Nominal
HIGHER
Higher levels of measurement have all the properties of lower levels of measurement.
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4. Nominal Scale Basic Measures of Comparisons Examples Average
Identity male-female mode
user-nonuser
occupations
uniform numbers
Which of the following soft drinks do you like? Check all that apply.
 Coca-Cola  Mountain Dew  Seven Up
 Dr. Pepper  Pepsi  Sprite
SLIDE 13-3

5. Ordinal Scale Basic Measures of Comparisons Examples Average
Order brand preference median
social class
hardness of minerals
lumber quality grades
Rank the following soft drinks from 1 (least liked) to 6 (most liked):
___Coca-Cola ___Mountain Dew ___Seven Up
___Dr. Pepper ___Pepsi ___Sprite
SLIDE 13-4

6. Interval Scale Basic Measures of Comparisons Examples Average
Comparison temperature mean
of intervals grade point avg.
brand attitude
company image
What is your overall opinion about each of these brands?
unfavorable favorable
Coca-Cola
Dr. Pepper
Pepsi
Sprite
SLIDE 13-5

7. Ratio Scale Basic Measures of Comparisons Examples Average
Comparison units sold geometric
of absolute # of purchases or
magnitudes age harmonic
income mean
Divide 100 points among these soft drinks according to your likelihood of purchasing each within the next week:
___Coca-Cola ___Mountain Dew ___Seven Up
___Dr. Pepper ___Pepsi ___Sprite
SLIDE 13-6

8. Hypothetical Construct
A concept used in theoretical models to explain how things work. Hypothetical constructs include such things as attitudes, personality, and intentions, concepts that cannot be seen but that are useful in theoretical explanations.
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9. The Problem of MeasurementC C C C
Observable Data C C
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10. Potential Sources of Variation in Scores
True differences in the characteristic being measured.
Differences in other relatively stable characteristics of the individual.
Differences due to temporary personal factors.
Differences due to situational factors.
Differences due to variations in administration.
Differences due to the sampling of items.
Differences due to lack of clarity of the measuring instrument.
Differences due to mechanical factors.
SLIDE 13-9

11. Variation in Obtained Scores
XO = XT + XS + XR
Where XO = obtained score
XT = true score
XS = systematic error
XR = random error
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12. Establishing the Validity of Measures
Predictive validity
Content validity
Construct validity
Reliability
SLIDE 13-11

13. Illustration of Random Error.
Old Rifle New Rifle That is Sighted in Accurately .
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14. Illustration of Systematic Error.
New Rifle That is New Rifle That is Sighted in Poorly Sighted in Accurately
SLIDE 13-13

15. Developing Measures Specify Domain of the Construct Purify Measure
Generate Sample
of Items
Assess Validity
Collect Data
SLIDE 13-14