Project Blue Book Special Report No. 14 (Analysis of Reports of Unidentified Aerial Objects)

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TABLE XI
CHI SQUARE TEST OF REVISED KNOWNS VERSUS UNKNOWNS
ON THE BASIS OF DURATION OF OBSERVATION
Adjusted
x2,
Duration of
Number of
Number of
Number of
(K-n} 2
Observation
KNOWNS
KNOWNS (K)
UNKNOWNS (n)
K
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5 sec or less
92
31
27
0.52
6-10 sec
47
16
21
1. 56
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11-30 sec
31-60 sec
118
92
40
31
33
42
1. 23
3.90
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61 sec-5 min
6 min-30 min
252
259
85
87
99
71
2. 31
2.94
Over 30 min
91
31
37
1. 16
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Not stated
335
113
104
0.72
Total
1286
434
434
14.34
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Degrees of freedom
5%
7
14. 1
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1%
18.5
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73
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