The Selection Process Between the Sampling Probabilities Plans
Examples for beginners Examples for advanced users
Example for beginners 1: obtain technical record and a list of units to investigate. Example for beginners 2: choose the methods with minor variance. Example for beginners 1: obtain technical record and a list of units to investigate. You need to obtain a sample, not superior to the 5% of the total, in order to begin an investigation of the set of clients by sampling. For this you have a data base with the following information:
Solution The data in the program are introduced by means of the option "Data." Inside the option "Sampling," you may select the method "Systematic with constant interval" and lastly obtain in the menu of "Listings," the units that are going to be in the sample and another ones that they could be used like substitutes for the case of absences and negative. In the screen "Report" you have prepared your technical record and the units that they should be investigated. Results Technical record of the Survey: Data of the design Population frame used: Companies clients of the firm. Variable of study: Purchases in the firm the previous year Auxiliary variable: social Capital Method of sampling: Systematic With Constant Interval
Units to investigate that have been selected the number 9 like aleatory of selection and using sampling systematic with constant interval: Population frame used: Companies clients of the firm Variable of study: Purchases in the firm the previous year Auxiliary variable: Social Capital
The values of the sample (9) identify the units, in this case companies that should be investigated in the survey. The other two columns represent the identifications of those substitutes or reservations units, that they will investigate only in case taht it is not possible investigate the unit originally selected. Parameters: Mean of population = 90.9825 Typical deviation (n-1) = 1503.6463 Typical deviation of the estimator = 4.5755 Sample size = 20 Example for beginners 2: choose the methods with minor variance. Now you are asked to select of all the available methods the one with minor variance. Solution In the option "Configuration" we selected all the methods. Later in "Calculations" we opted for the option" Variances for selection of methods." In the window "Reports" we have the recommendation, from the system, to choose the method . Results
Comment In the report the program recommends use the method of two balanced conglomerate, that presents the minor variances and that it is 16.5. The centered methods are not recommended for considerations of great variability of the methods that should study in the most advanced examples. The same report recommends:
From this table we observe that, in the case of not needing to calculate the errors of sampling with the data of a single sample, the better method will be the systematic with variable interval. Also could be observe that the variances of the method (4) present a certain variability consequence of not calculating the whole sampling space and to base the calculations in a representation of the same. Lastly, the software, recommended the systematic sampling with variable interval. |