Dr. David Saunders
"Before it was over I had worked out a comprehensive scheme of coding, and some 7,500 reports were processed - I was shooting for the 10,000 mark to provide a good basis for statistical analysis. However, even when we had only a few hundred reports coded and collated in the "Sighting Catalog" it was possible to see some interesting differences in the quality of reports arriving from different sources, and it was even more interesting to consider these in the light of the question network that might have been used to screen out fake UFOs.
"For example, a very basic question is the duration of a sighting. Very brief sightings are apt to be meteors or jet aircraft, and even if they are UFOS, they are unlikely to contribute much information. Very extended sightings are most apt to be balloons (in the daytime) or astronomical objects (at night). Therefore, there is an optimal duration for a UFO sighting, about five to fifteen minutes - long enough to observe something worth reporting, but not too long. When I made distributions of the durations associated with Blue Book and NICAP reports, since these were then our only sources of routine "unselected" reports, I was struck by the difference in the distributions. Blue Book had a much higher proportion of extremely short durations and also a noticeably higher proportion of extremely long durations, suggesting that they were dealing with a potentially more explainable collection of reports. NICAP'S reports included a much higher proportion in the middle range of durations that would interest us. Had I then been in a position to make comparisons based on other relevant features of the reports - for example, reported colors, time of day, apparent size, number of details - I am sure similar patterns would have emerged.
"What I did do next was to go through the computer listings to see what proportion of the current reports were coming to us by way of more than one channel The result of this exercise did much to explain the results of the previous one. The only sightings that we heard about from both Blue Book and NICAP were sightings that had achieved enough publicity for us to have heard about them also from still other sources - either press notices or telephone calls. Except for the overlap created by this relatively small number of notorious cases, the Blue Book and NICAP samples were completely different."
David R. Saunders
Source: "UFOs? Yes! - Where the Condon Committee Went Wrong", 113