Project Blue Book Special Report (second copy)

Another interesting aspect of these new tests is that there are only
two large discrepancies in all of the groups. These are for the 11 or more
groups in the classification by number of objects per sighting and for the
over-400-mph and meteor-like group for the classification by speed. The
first was relatively unchanged by deletion of the astronomical sightings
principally because of the concentration of sightings in the single-object
category. The second was slightly increased by the removal of the astro-
nomical sightings from the meteor-like classification. However, the main
discrepancy, that of the excess of UNKNOWNS in the over-400-mph class,
was little changed.
The results of these tests are inconclusive since they neither confirm
nor deny that the UNKNOWNS are primarily unidentified KNOWNS, although
they do indicate that relatively few of the UNKNOWNS are actually astro-
nomical phenomena.
It was decided that this process would not be carried to its logical
conclusion (that is, the determination of a linear combination of KNOWNS
that would give a negligible chi square when compared with the UNKNOWNS),
since it was felt that the inaccuracies in the reports would give a distorted
and meaningless result.
The "Flying Saucer" Model
The importance of the problem dictated a second approach, should the
statistical results prove inconclusive. It was decided that an attempt
would be made to describe the physical appearance, flight characteristics,
and other attributes (that is, construct a model) of a class or classes of
"flying saucers".
Preparatory to this attempt, are-evaluation of the UNKNOWNS was
necessary. This re-evaluation was accomplished by a panel composed only
of persons previously associated with the work. Using all the UNKNOWNS
reports available at ATIC, the panel made a careful study of the reports for
the UNKNOWN SIGHTINGS in angle-of-sun-elevation Groups 1, 2, 3, 6, and
7 — those groups for which the sun was either above the horizon or less than
10° in elevation below the horizon.
This study had two purposes. The first was to determine, with
additional information such as the angle of elevation of the sun, how many
of the UNKNOWNS might be ascribed to known phenomena. The second was
to obtain those UNKNOWNS which were described in sufficient detail that
they might be used to construct a model or models of "flying saucers".
It was decided to put any of the UNKNOWNS which might be known
phenomena into a "possible KNOWN" category to denote the slightly lower
confidence level which could be ascribed to these new evaluations. The
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