Sampling Statistics Guide. Author: Ali Fadakar

Size: px

Start display at page:

Download "Sampling Statistics Guide. Author: Ali Fadakar"

Adele Simmons
5 years ago
Views:

1 Sampling Statistics Guide Author: Ali Fadakar

An Introduction to the Sampling Interface Sampling interface is an interactive software package that uses statistical procedures such as random sampling, stratified random sampling, one-stage cluster

2 An Introduction to the Sampling Interface Sampling interface is an interactive software package that uses statistical procedures such as random sampling, stratified random sampling, one-stage cluster sampling, two-stage cluster sampling and sampling with varying probability. In general, the software includes a sampling window. The sampling window consists of two tabs, Data Sheet view and Output view. File A new project is automatically created when the software is launched. You can also open a new project by clicking File> Add New Project. In general, use the File menu commands to manage projects. Open a previously saved project using the File>Open command. Click File>Open. Use the file browser to find the Sampling (*.sa) project file. By default, files that can be opened or translated by Sampling are displayed. Then, select the file you want to open and click Open. To save an existing, active project with a new name or to a new location: Click File>Save As. Use the file browser to find the directory where you want to save the file. Then, type the name of the file in the File name box and click Save. Use the File>Save command to save the active project. Display 1: File menu.

Inserting Data The first step is to insert Data into the active project. To enter data right-click in the window and select Add new column then enter the name for column and press Space or Enter.

3 Inserting Data The first step is to insert Data into the active project. To enter data right-click in the window and select Add new column then enter the name for column and press Space or Enter. After that, you can enter your data. Between data entry, you must press at least one Space or Enter. Note1: The columns can have the same name or even can be without a name. Note2: Some special characters such star, decimal point and minus sign cannot be used for the column name. To import datum several times, a panel on the left side of the Data Sheet tab can be used. The value should be entered in the Value box and the number of iterations should be entered in the Frequency box and then press Enter or Ok button. For example, in Display 2, two data with value 3 are added to the first column named "a". The size of writing is determined by the zoom box. The default size is two, the minimum and maximum allowed values are respectively one and ten. Display 2: Data Sheet tab. Edit Data In the Data Sheet tab, the data and the name of columns cannot be deleted or edited. However, these advantages can be done by clicking Edit>Edit Column. This opens the dialogue box shown in Display 3.

Display 3: Edit column. Select the number of the column that you want to edit it by the Column Number box. You can change the Column s Name in Column Name box.

4 Display 3: Edit column. Select the number of the column that you want to edit it by the Column Number box. You can change the Column s Name in Column Name box. Also, you can edit or add data to the specified column in Data box. Finally, click Ok button and the contents of the selected column will be changed according to the edition. Moreover, the data can be inserted in the form of fraction or multiplication of two numbers without spaces in the Data box. For example, if you type 1/5 in the Data box, 0.2 will be displayed on the main datasheet tab. Recode into Different Column Click Edit>Recode into Different Column. This opens the dialogue box shown in Display 4. You can define values to recode in this dialog box. Select the number of the column by the Column box. You can specify a name for the new column in the Name box. In the Old Value panel, you can specify the type of value that you wish to recode (e.g., a specific Value, a Range of values, or All Other). All Other can be applied to any value that not explicitly accounted by the previous recoding rules and it should be applied at the end. In the New Value panel, you can specify the new value for column (i.e., a specific numeric code such as 2, or copy old values). In the Old->New panel, click Add button to add the item. The recode that you have specified appears in Old->New box. If you need to remove one of the recodes that you have added to the Old->New box, simply click on it and then click the Remove button. When you have finished defining the conditions, click Ok button.

Display 4: Recode into Different Column. Random Sampling Click Analyze>Random Sampling. The Random Sampling dialog box is displayed. This dialogue box is shown in Display 5.

5 Display 4: Recode into Different Column. Random Sampling Click Analyze>Random Sampling. The Random Sampling dialog box is displayed. This dialogue box is shown in Display 5. Select the columns under the headings Column(s). If your sample brings with the replacement you should check Sampling with replacement box in this window and you can determine the size of your statistical society in the N box. The sample size estimation output is controlled via the Estimation n button (Display 6). The sample size can be determined to estimate either population mean or population proportion. The Proportion option is used when the data of the selected column are 0 and 1. To obtain an estimator p having probability at least 1 α of being no farther than d from the population proportion, the sample size formula based on the normal approximation gives: Pr( p-p <d) =1- α 2 2 n = Np(1 p)/[ (N 1)(d /z ) + p(1 p)] In the Mean option, you can specify confidence interval in the 2*l box for sample size estimation. In this procedure the sample mean y is an unbiased estimator of the population mean μ with variance var( y ) = (N n) 2 /Nn. Setting: 2 s z N n nn and solving for n gives the necessary sample size: = 2 l

n 1 1 2 2 2 d z 1 N 1 n0 1 N 2 2 z Where n0.

6 n d z 1 N 1 n0 1 N 2 2 z Where n0. If instead of confidence interval 2*l, you select an amount in r box for 2 d relative error (the difference between the estimate and the true value, divided by the true value) the criterion to be met is: Pr( (Y n Y N) >r) = α Y N and the sample size formula is: n r z 1 N Display 5: Random Sampling.

7 Display 6: Estimate n. An output of a command Random Sampling Display 7 shows the Random Sampling Output, you can see, for example, the mean of the sample in line 1, the variance of mean in line 2, the confidence interval in line 3, the sample size in line 4 and the estimation of sample size according to the confidence interval option in line 5. Display 7: Output of Random Sampling.

Stratified Random Sampling To select Stratified Random Sampling click Analyze>Stratified Random Sampling. Display 8 shows the Stratified Random Sampling dialogue box.

8 Stratified Random Sampling To select Stratified Random Sampling click Analyze>Stratified Random Sampling. Display 8 shows the Stratified Random Sampling dialogue box. A source columns list is a list of columns from the data sheet that can be used in the requested analysis. Each column is considered as one Stratum. You can specify the columns under the headings Stratums. Note you should have more nh Nh than one Stratum. If sampling is proportional allocation, you should check the n N Proportional Allocation box. Then the box N appears above the check box. The size of the statistical society should be specified in this box. Display 8: Stratified Random Sampling. If the sampling is not proportional allocation, after specifying the columns under the headings Stratums, by double-clicking on the Stratums list, the window will become as shown in Display 9.

9 Display 9: Stratified Random Sampling after double-click. You should specify the size of statistical society for each stratum and then press Enter or click Ok button. Finally, click Continue button. Display 10: Optimum Allocation.

The Optimum Allocation output is controlled via the Optimum Allocation button (Display 10). You must specify cost sampling unit for each Stratum and then press Enter or click Ok button.

10 The Optimum Allocation output is controlled via the Optimum Allocation button (Display 10). You must specify cost sampling unit for each Stratum and then press Enter or click Ok button. If the cost of sampling unit for each Stratum is unique, you should check NEYMAN Allocation and specify an amount of cost. If an amount of variance is specified, you should select the Variance confirm box and specify the amount of variance. If an amount of total cost is specified, you should select the Cost confirm box and specify the amount of cost. One Stage Cluster Sampling To select the one-stage cluster sampling click Analyze>One Stage Cluster Sampling. Display 11 shows the One Stage Cluster Sampling dialogue box. Display 11: One Stage Cluster Sampling. A source columns list is a list of columns from the Data sheet that can be used in the requested analysis. Each column is considered as one Cluster. Total number of clusters should be determined by the N box and the mean size of clusters should be determined by the M box. Then click Ok button. Two Stage Cluster Sampling The two-stage cluster sampling procedure can be accessed by selecting Analyze >Two Stage Cluster Sampling. Display 12 shows the Two Stage Cluster Sampling dialogue box.

Display 12: Two Stage Cluster Sampling. A source columns list is a list of columns from the Data sheet that can be used in the requested analysis. Each column is considered as one Cluster.

11 Display 12: Two Stage Cluster Sampling. A source columns list is a list of columns from the Data sheet that can be used in the requested analysis. Each column is considered as one Cluster. Total number of Clusters should be determined by the N box and the mean size of Clusters should be determined by the M box. If clusters have the same size, you should check Cluster of Equal Sizes. Otherwise, by double-clicking on the Cluster, the dialog box will become as shown in Display 13.

Display 13: Two Stage Cluster Sampling after double-click. You should specify the size of statistical society for each cluster and then press Enter or click Ok button. Then click Continue.

12 Display 13: Two Stage Cluster Sampling after double-click. You should specify the size of statistical society for each cluster and then press Enter or click Ok button. Then click Continue. Sampling with Varying Probability You can proceed to apply the probability sampling with varying by clicking Analyze>Sampling with Varying Probability. Display 14 shows the Sampling with varying probability dialogue box.

Display 14: Sampling with Varying Probability. Specify the data columns and the probability of data columns under the headings Column(s) and probability(s) respectively.

13 Display 14: Sampling with Varying Probability. Specify the data columns and the probability of data columns under the headings Column(s) and probability(s) respectively. Note that the displacement in the columns in the probability(s) or Column(s) boxes may change the correspondence of the data to their probability value. If your sample brings without replacement you should check the Sampling without replacement box and you should determine the size of your statistical society in the N box.

General Guidelines: SAS Analyst

General Guidelines: SAS Analyst The Analyst application is a data analysis tool in SAS for Windows (version 7 and later) that provides easy access to basic statistical analyses using a point-and-click