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

Special Report No. 14 was issued by the U.S. Air Force's Air Technical Intelligence Center on 5 May 1955. It is a statistical study of about 4,000 reports of unidentified aerial objects from June 1947 to December 1952. The reports were reduced to IBM punched cards and analyzed with methods including chi square tests. The report concludes that the reports it examined are very unlikely to represent technology beyond present scientific knowledge, and it notes that no case produced valid physical evidence.

TABLE XI CHI SQUARE TEST OF REVISED KNOWNS VERSUS UNKNOWNS
ON THE BASIS OF DURATION OF OBSERVATION
Duration of
Observation
Number of
KNOWNS
Adjusted
Number of
KNOWNS (K)
Number of
UNKNOWNS (n)
X 2 ,
K
0.
1.
1.
3.
2.
2.
1.
0.
52
56
2 3
90
31
9 4
16
72
5 sec or less
6-10 sec
11.-30 sec
31-60 sec
61 sec-5 min
6 min-30 min
Over 30 min
Not stated
92
47
118
92
252
259
91
335
Total 1286
31
16
40
31
85
87
31
113
434
27
21
33
42
99
71
37
104
434 14. 34
Degrees of freedom
5%
1%
14. 1
18. 5
73
gfc :-•