For equal or unequal delivery errors and an offset point of aim, the chance that th~ burst point of a warhead occurs within a given distance of a selected point of the target is approximated by reference to the Non-central Chi-square distribution. Oftset circula~ and non-circular probabilities of hitting for the two and three dimensional cases may thus be approximated with a single, s traight-forward and rather simple technique by the u~e of a central Chi-square distribution with fractional

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... er of degrees of f r eedom or a transformation to approximate Normality. Computationo of probabilities of hitting are illustrated by examples. The approxi~t ions r ecommended appear to be of sufficient accuracy for many weapon syst~ms evaluation problems . This report supers edes BRL M emorandum Report No. 11((2.