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Việc phân chia một mẫu quan sát vào một số lớp học, cùng với số lượng quan sát trong mỗi lớp. Hành vi như là một bản tóm tắt hữu ích của các tính năng chính của dữ liệu, chẳng hạn như hình dạng, vị trí và lây lan. Một ví dụ về một bảng được đưa ra dưới đây: | individuals having a weaker heart or a greater genetic disposition for cancer. Everitt B. S. 2003 Modern Medical Statistics Arnold London. Framingham study A long-term investigation begun in Framingham Massachusetts in 1948 to identify the relation of possible risk factors to the occurrence of chronic circulatory disease and to characterize the natural history of the disease. American Journal of Public Health 1957 47 4-24. Frequency distribution table The division of a sample of observations into a number of classes together with the number of observations in each class. Acts as a useful summary of the main features of the data such as location shape and spread. An example of such a table is given below Hormone assay values mmol l Class limits Observed frequency 75-79 1 80-84 2 85-89 5 90-94 9 95-99 10 100-104 7 105-109 4 110-114 2 115 1 See also histogram and cumulative frequency distribution. Frequency polygon A diagram used to display graphically the values in a frequency distribution. The frequencies are graphed as ordinate against the class midpoints as abscissae. The points are then joined by a series of straight lines. Particularly useful in displaying a number of frequency distributions on the same diagram. Figure 40 gives an example. Frequentist inference An approach to statistics based on a frequency view of probability in which it is assumed that it is possible to consider an infinite sequence of independent repetitions of the same statistical experiment. Significance tests hypothesis tests and likelihood are the main tools of this form of inference. See also Bayesian methods. Frequentist inference Still the form of inference used most commonly by clinical researchers but increasingly challenged by Bayesian inference now that the latter can be applied almost routinely. Friedman s two-way analysis of variance A distribution-free method that is the analogue of the analysis of variance for a design with two factors. Can be applied to data sets that do not .
