Issues in Measurement
Reliability and Validity
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Levels of Measurement
• Nominal
– Gender
– Favorite Brand
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Levels of Measurement
• Ordinal
– Class rank
– Challenge for Charity results
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Levels of Measurement
• Interval
– GMAT score
– Intention to purchase scale
– Likert scales
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Levels of Measurement
• Ratio
– Temperature in Kelvin
– Gross sales
– Height, weight, volume
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Reliability and Validity
Total Variance = True Information + Systematic
Error + Random Error
Reliability = True Information + Systematic
Error
Validity = True Information
Many times you need several measures to capture
what you want to measure.
Think about measuring purchase intentions.
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A Scale of Purchase Intention
1.
How likely are you to buy Pespi Cola on your next shopping trip? (circle one)
Very Unlikely 1
2
3
4
5
6
7
Very Likely
2.
Out of the last ten shopping trips
on how many times do you believe you purchased Pepsi Cola? (circle one)
0
1
2
3
4
5
6
7
9
10
3.
On how many of your next ten shopping trips
do you believe you will purchase Pepsi Cola? (circle one)
0
1
2
3
4
5
6
7
8
4.
How much do you like Pepsi Cola? (circle one)
Like
Very Little
1
2
3
4
5
6
7
9
10
Like A
Great Deal
5.
Think about your most preferred and least preferred soft drinks.
Where does Pepsi Cola fall on a scale that goes from your
most preferred to you least preferred soft drinks? (circle one)
Most Preferred
Least Preferred
Soft Drink
1
2
3
4
5
6
7
Soft Drink
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Example of Cronbach’s 
Cronbach’s  reflects the internal consistency of the
items within a scale. It is also the average of all split-half
correlations in a scale.
For a scale with K items Cronbach’s  is:
K


2
i



K 


1  K i 1 K

K  1
2
   i  2    ij 
 i 1

i j
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Variance Covariance Matrix Among Measures of Intent to Purchase
Scale Item
1
2
3
4
5
6
7
1
1.43
0.89
0.57
1.10
0.89
0.84 0.84
2
0.89
1.27
0.53
0.86
0.70
0.84 0.84
3
0.57
0.53
1.06
0.82
0.68
0.84 0.84
4
1.10
0.86
0.82
1.85
1.32
0.84 0.84
5
0.89
0.70
0.68
1.32
2.45
0.84 0.84
6
0.84
0.84
0.84
0.84
0.84
1.61 0.84
7
0.84
0.84
0.84
0.84
0.84
0.84 1.61
Diagonal All Entries Ratio
K/(K-1)
Cronbach's
Alpha
Original 5 Measures
8.06
24.78
0.33
1.25
0.84
All 7 Measures
11.28
46.48
0.24
1.17
0.88
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2)
Please evaluate the Virtual Adventures ride (Loch Ness Expedition)
(Please circle the appropriate answer).
Not At All
Very Much
Fun
1
2
3
4
5
Exciting
1
2
3
4
5
Challenging
1
2
3
4
5
Engaging Story
1
2
3
4
5
Unique Experience
1
2
3
4
5
Easy to Understand
1
2
3
4
5
Easy to Play
1
2
3
4
5
Family Fun
1
2
3
4
5
Total Enjoyment
1
2
3
4
5
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q2a
q2b
q2c
q2d
q2e
q2f
q2g
q2h
q2i
q2a q2b
q2c q2d q2e
q2f
q2g q2h
0.58
0.42 0.84
0.25 0.32 0.68
0.22 0.31 0.24 0.85
0.20 0.25 0.25 0.31 0.58
0.22 0.19 0.03 0.19 0.22 1.14
0.18 0.21 0.01 0.21 0.18 0.76 1.07
0.23 0.23 0.09 0.21 0.19 0.24 0.33 0.69
0.35 0.42 0.28 0.27 0.24 0.25 0.25 0.28
Sum
Sum
k Var Covariances Alpha
9 6.96 9.03
0.81
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q2i
0.53
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