Đặc biệt quan trọng trong nghiên cứu AIDS, kể từ khi các dữ liệu giám sát AIDS cần phải được sửa chữa một cách thích hợp cho việc báo cáo chậm trễ trước khi họ có thể được sử dụng để phản ánh tỷ lệ mắc AIDS. Xem cũng trở lại chiếu. | distributions for example Student s t-distribution and the F-distribution. Altman D. G. 1991 Practical Statistics for Medical Research Chapman and Hall CRC Boca Raton FL. Delay distribution The probability distribution of the delay in reporting an event. Particularly important in AIDS research since AIDS surveillance data need to be corrected appropriately for reporting delay before they can be used to reflect current AIDS incidence. See also back-projection. Philosophical Transactions of the Royal Society of London Series B 1989 325 135-45. Delta technique A procedure for finding means and variances of functions of random variables. Dunn G. 2004 Statistical Evaluation of Measurement Errors Arnold London. Demography The study of human populations with respect to their size structure and dynamics. The aim of formal demographic analysis is to isolate the components of demographic patterns by dividing a population into relatively homogeneous subgroups with analysis by age and sex generally being of greatest importance. Bangarats J. Burch T. and Warchter K. 1987 Family Demography Methods and their Applications Clarendon Press Oxford. Dendrogram A term encountered in the application of agglomerative hierarchical clustering methods. Refers to a tree-like diagram that describes the stages in the clustering process as individuals and then groups are joined together to form fewer larger clusters. Examples of such a structure are shown in Figure 30. See also group average clustering single linkage clustering and Ward s method. Everitt B. S. Leese M. and Landau S. Cluster Analysis 4th edn 2001 Arnold London. Density sampling A method of sampling controls in a case-control study that can reduce bias due to possibly changing patterns in exposure. Controls are sampled from the population at risk over the period of accrual of the cases rather than simply at one point in time such as the end of the period. American Journal of Epidemiology 1982 116 547-53. Dependent variable See .
