Project Blue Book Special Report (second copy)

SUMMARY
Reports of unidentified aerial <5bjects (popularly termed "flying
saucers" or "flying discs", have been received by the U. S. Air Force
since mid-1947 from many and diverse sources. Although there was no
evidence that the unexplained reports of unidentified objects constituted
a threat to the security of the U. S. , the Air Force determined that all
reports of unidentified aerial objects should be investigated and evaluated
to determine if "flying saucers" represented technological developments
not known to this country.
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In order to discover any pertinent trends or patterns inherent in the
data, and to evaluate or explain any trends or patterns found, appropriate
methods of reducing these data from reports of unidentified aerial objects
to a form amenable to scientific appraisal.were employed. In general, the
original data upon -which this study was based consisted of impressions and
interpretations of apparently unexplainable events, and seldom contained
reliable measurements of physical attributes. This subjectivity of the data
presented a major limitation to the drawing of significant conclusions, but
did not invalidate the application of scientific methods of study. .
The reports received by the U. S. Air Force on unidentified aerial
objects were reduced to IBM punched-card abstracts of the data by means
of logically developed forms and standardized evaluation procedures.
Evaluation of sighting reports, a crucial step in the preparation of the data
for statistical, treatment, consisted of an appraisal of the reports and the
subsequent categorizing of the object or objects described in each report.
A detailed description of this phase of the study stresses the careful
attempt to maintain complete objectivity and consistency.
Analysis of the refined and evaluated data derived from the original
reports of sightings comprised (1) a systematic attempt to ferret out any
distinguishing characteristics inherent in the data or any of their segments,
(2) a concentrated study of any trends or patterns found, and (3) an attempt
to determine the probability that any of the UNKNOWNS represent obser-
vations of a class, or classes, of "flying saucers".
The first step in the analysis of the data revealed the existence of
certain apparent similarities between cases of objects definitely identified
and those not identified. Statistical methods of testing were applied -which
indicated a low probability that these apparent similarities were signifi-
cant. An attempt to determine the probability that any of the UNKNOWNS
represent observations of a class, or classes, of "flying saucers" neces-
sitated a thorough re-examination and re-evaluation of cases of objects not
originally identified; this led to the conclusion that the probability was very
small. v
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