Probability distributions and search schemes

One property of search schemes used frequently as an indication of search efficiency is the expected number of passes (or read operations) required to locate a record in computer memory (or secondary storage). However, other properties related to the variation in the number of passes required may be equally important in determining the most efficient search technique for a given file (or set of records). These properties can be obtained from the distribution of the number of passes.

In this paper, the binary search scheme is discussed within this framework. The probability distribution of the number of passes required is derived along with the mean, standard deviation and the percentiles. The mean and standard deviation of the random sequential search scheme are also presented. The application of these results to common search problems in record access and retrieval are discussed and possible extensions involving a combination of binary and random search techniques are indicated.