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<br />analysis of precipitation changes recommended for the first year stated <br />as hypotheses in the CSU design study are as follows: <br /> <br />1. Seeding material released from ground generators being used <br />1n the present Utah weather modification program can reach seedable <br />cloud locations in the desired concentration levels to affect significant <br />parts of storms being seeded. <br /> <br />2. Sufficient supercooled water is present in storms (or portions <br />of storms) over the rtah mountains to permit seeding material to nucleate <br />and form additional precipitation. <br /> <br />3. Growth times and trajectories of the affected <br />(natural or artificially produced) are appropriate to <br />mountain slopes in the intended mountain area. <br /> <br />ice particles <br />intercept the <br /> <br />Another hypothesis, not directlv stated 1n the CSU design study, <br />refers to the statistical analysis of precipitation changes during the <br />several years of operation. That is, <br /> <br />4. Precipitation during the project period has been significantly <br />greater than what would have occurred in the absence of seeding. <br /> <br />In reporting the research and evaluation carried out on the Utah <br />operational project, two important factors should be recognized at this <br />point. The first factor is that the use of randomization was not <br />available. Although the USU proposal called for randomization, it <br />was later deleted due to operational considerations. Yet the need for <br />limited randomization is great when evaluation of operational projects is <br />being made. Only when randomization is used can assurance be given that <br />in the long run the treated and untreated events are from the same <br />population of cloud systems. <br /> <br />Consequently, there are many aspects of the present evaluation <br />that are affected by this difficulty. Even though var10US comparisons <br />between unseeded and seeded cloud or precipitation parameters are <br />made, there remains the question of whether the comparisons are between <br /> <br />3 <br />