Project Blue Book Special Report (second copy)

This is Project Blue Book Special Report No. 14, "Analysis of Reports of Unidentified Aerial Objects," Project No. 10073, dated 5 May 1955. The study reduced about 4,000 sighting reports received by the U.S. Air Force between June 1947 and December 1952 to IBM punched cards and analyzed them statistically, including chi square tests comparing knowns with unknowns. It concludes that the reports very probably do not represent technological developments beyond present scientific knowledge, and it notes that no case produced physical evidence.

TABLE V CHI SQUARE TEST OF KNOWNS VERSUS UNKNOWNS
ON THE BASIS OF DURATION OF OBSERVATION
Duration of
Observation
5 sec or less
6-10 sec
11-30 sec
31-60 sec
61 sec-5 min
6-30 min
Over 30 min
Not stated
Number of
KNOWNS
259-"
92
153
108
269'
305
135
444
Adjusted
Number of
KNOWNS (K)
64
23
38
26
66
75
33
109
Number of
UNKNOWNS (n)
27
21
33
42
99
71
3 7 l
104
X 2
(K-n)2
K
21.39
0. 17
0.66
9.85
16. 50
0.21
. 0.48
0.23
Total 1765 434 434 49.49
# Degrees of freedom
5%
1%
14. 1
18. 5
65
it I