THE object of sequential sampling is to reduce the size of the sample which must be drawn to reach a decision about a population within specified limits of error. The classical sampling method is to draw a sample of predetermined size and to examine each member after the complete sample has been obtained. The sequential method performs the operation, so to speak, in reverse by choosing the sample one by one until a point is reached at which the decision can be taken within predetermined limits of error. The sample size is thus not an assigned number but varies from one sample to another, according to the way in which the observations run. Sequential Analysis of Statistical Data Applications. Prepared by the Statistical Research Group, Columbia University, for the Applied Mathematics Panel, National Defense Research Committee, Office of Scientific Research and Development. (SRG Report 255.) Pp. xxix + 287, (New York: Columbia University Press ; London: Oxford University Press, 1945.) 42s. net.