Nature of physical problem University of Belfast, N. Ireland (see application form in The problem is to determine the frequency function P(n) of this issue) the posterior probability that a small sample of a radioactive isotope R contains n atoms at the end of the production of R, Computer: UNIVAC 1108 Installation: State Computer Centre, when the counts in the subsequent counting periods are known. Helsinki. Method of solution Operating system: EXEC-8 First, P(n) is computed for the beginning of the last counting period by a Bayesian method. Then P(n) is used for computing Programming language used: ASA FORTRAN a new P(n) for the beginning of the preceding interval, if there was an interval. Then P(n) is computed in the same way for High speed storage required: 25067 words. the beginning of the preceding counting period, and so on. Mixed probability distributions are used for taking into ac-No. of bits in a word: 36. count uncertainty in the efficiency and background rate of the detector. Overlay structure: none. Restriction on the complexity of the problem No. of magnetic tapes required: none. n ~129. Otherperipherals used: Card reader and line printer Typical running time 32 s (20 s CPU) on UNIVAC 1108. No. of cards in combined program and test deck: 123. Unusual features of the program Card punchingcode: IBM 29.
The repetitive application of Bayes's method to the multiple branches of possibilities, and the built-in a priori constraint n ~0, which reduces the error estimates.