http://manuals.pqstat.pl/ 2026-04-10T23:54:40+00:00 http://manuals.pqstat.pl/ http://manuals.pqstat.pl/lib/tpl/dokuwiki/images/favicon.ico text/html 2022-02-15T17:26:24+00:00 Anonymous (anonymous@undisclosed.example.com) http://manuals.pqstat.pl/en:statpqpl:wielowympl:wielorpl:analrpl Analysis of model residuals To obtain a correct regression model we should check the basic assumptions concerning model residuals. * Outliers The study of the model residual can be a quick source of knowledge about outlier values. Such observations can disturb the equation of the regression to a large extent because they have a great effect on the values of the coefficients in the equation. If the given residual text/html 2022-02-15T17:21:16+00:00 Anonymous (anonymous@undisclosed.example.com) http://manuals.pqstat.pl/en:statpqpl:wielowympl:wielorpl:morepl More information about the variables in the model * Standardized -- In contrast to raw parameters (which are expressed in different units of measure, depending on the described variable, and are not directly comparable) the standardized estimates of the parameters of the model allow the comparison of the contribution of particular variables to the explanation of the variance of the dependent variable text/html 2023-04-01T18:24:56+00:00 Anonymous (anonymous@undisclosed.example.com) http://manuals.pqstat.pl/en:statpqpl:wielowympl:wielorpl:predpl Model-based prediction and test set validation Validation Validation of a model is a check of its quality. It is first performed on the data on which the model was built (the so-called training data set), that is, it is returned in a report describing the resulting model. In order to be able to judge with greater certainty how suitable the model is for forecasting new data, an important part of the validation is to become a model to data that were not used in the model estimation. If the summa… text/html 2023-03-31T19:10:52+00:00 Anonymous (anonymous@undisclosed.example.com) http://manuals.pqstat.pl/en:statpqpl:wielowympl:wielorpl:przykl Example for multiple regression EXAMPLE (publisher.pqs file) A certain book publisher wanted to learn how was gross profit from sales influenced by such variables as: production cost, advertising costs, direct promotion cost, the sum of discounts made, and the author's popularity. For that purpose he analyzed 40 titles published during the previous year (teaching set). A part of the data is presented in the image below: text/html 2024-12-06T09:17:54+00:00 Anonymous (anonymous@undisclosed.example.com) http://manuals.pqstat.pl/en:statpqpl:wielowympl:wielorpl:weryfpl Model verification * Statistical significance of particular variables in the model. On the basis of the coefficient and its error of estimation we can infer if the independent variable for which the coefficient was estimated has a significant effect on the dependent variable. For that purpose we use