Sub Samples

Sub Samples

In the hierarchy column, either right-click on the Sub Samples item then select Edit from the drop-down menu, or double-click on the item, to open its editor page - .

Figure 1 - Example of the editing page for the Sub Samples folder

The "main" Sub Samples folder has the following data fields in its editing page:

• Disregard Sampling Matrix... - you can set up universal criteria with matrices etc. (go to Filter Overview for more information). Check this box to switch off the requirement to use matrices and only use the filters. Set the filters for each group, sub-sample etc. individually. This method of sampling is called Basic Sampling.
• Matrix List - this is the list of matrices that are available in the Matrix drop-down on the Sub Sample editor page. This allows you to create a small set of matrices from the complete list (which may run into hundreds), thereby simplifying the selection process and reducing the chance of errors. Click Add, then select the required matrices from the list.
• Custom Code - use this field to add custom codes to the job so you can use the codes later in the sub samples.
• Global Custom Code - use this field to add custom codes to the job that all in the sample will be given (this is similar to the default codes in the sub sample).

Adding a Matrix List

A panel can have a large number of matrices available for use. When you are setting up a group of sub-samples you may only need a small selection of the available matrices. Use the Matrix List functionality to build a “short list” of the matrices that are to be available for the sub-samples. These matrices will then appear in the drop-down list beside the Matrix field on the sub-sample editor page.

To add a matrix to the drop-down list, click the Add Matrix button and select the required matrix from the full list.

Editing Sub Sample Folders

In the hierarchy column, either right-click on a sub-sample folder then select Edit from the drop-down menu, or double-click on the folder, to open the folder's editor page - .

Figure 2 - Example of the editing page for a sub sample folder

In the figure above, note the two "CustomCode" fields in the lower part of the page. These are created in the Sub Samples editing page.

The Sub-folders have the following data fields in their editing pages:

• Sub Sample Name – the name for the sub sample.
• Selected Matrix – the matrix to be used to build up the group. Note that the matrix must be created first. The drop-down list will contain those matrices added to the Matrix List in the Sub Samples editing page.
• Manage Available matrices - click this link to go to the Sub Samples Folder Editor Page to manage the matrices.
• Use Dynamic Targets - check this box if you wish to set the segment targets according to the composition of the underlying sampling population (BitStream set).
• Apply Filters when Calculating Dynamic Targets - check this box if you wish to include the sampling job's universal criteria and the sub-sample filter in the query to calculate the dynamic segment targets.
• Cellweight – select the cell weight to be used by the Sub Sample. See also Original Cellweight below.
• Original Cellweight – the customer might have specified a particular cell weight. However if not enough respondents can be found who satisfy the selection criteria, the cell weight might be changed to enable the job to be completed. In that case the cell weight actually used is given in the Cellweight field while the cell weight specified by the customer is given here.
• Expression – the filter used to select the respondents. Click the … button to open the Expression Editor window (go to Creating an Expression for more information).
• Total target – this is the total number of panelists you wish to have in the sub sample Each group set in the sub sample is allocated its own target, and this total target is the total of the group set targets. Forsta Plus will attempt to fill this requirement while adhering to the selection criteria set in this and the other tabs.

Note: Forsta Plus performs two series of checks while creating a sample. The first check is performed using the criteria defined in the sampling job (using the Universal Criteria expression and exclusions), then a second check is performed to ensure any required percentages, weightings etc. are met. If Forsta Plus finds more than the required number of panelists that comply with the criteria then the program will randomly select the total required from those found. If not enough panelists complying with the criteria in the first check can be found, then an error message is displayed and the job will stop. If you wish to continue with the job you will then have to change some of the criteria. If the first check finds enough panelists but the second check cannot meet the required percentages, weightings etc. then Forsta Plus will try to complete the job by making adjustments to the weightings and percentages. Any changes will be notified in the job report.

• Default Code – you can define a code number for each group. If a respondent is found who satisfies the general criteria but who does not fit into a specific group, they will be allocated this default code.
• <custom code> - if a custom code is defined in the sub-sample, then it will appear here. Add a value as required.
• Weight Parameter – this property is only used during concurrent sampling (go to Concurrent Sampling Overview for more information), and is only visible on the Sub Sample Editor page if the Expected Return Variable box is set to a value other than None. The property enables you to specify the accuracy of the sampling by using the probability that panelists are likely to reply to the survey. Enter a value between -1 and +1. A value of -1 will allow the sample to include panelists who have a low probability of replying. This will thereby result in a larger sample to ensure the required number of responses are returned. A value of +1 will restrict the sample to only those panelists who have a high probability of replying to the survey. This will thereby result in a sample closer in number to the required size.
• Disable Balancing – a particular matrix can be used for many jobs. Check this box if you do not want to use the cell weights applicable to the matrix.
• Discard Default Group… – check this box if you do not wish to use potential respondents who have been allocated the default code number (see above).

Creating a New Sub Sample

Note: A rule that creates BitStream files from the panel database must be created before sub samples can be created (go to Creating a New Rule for more information). For this rule, the Source must be Panel Database, the Target must be BitStream, and SurveyStatus must be selected in the Survey History Variables field.

1. Click on the Sub Sample icon after which you wish to create the new sub sample.
2. Click the right mouse button.

The right-click menu opens.

3. Click Add Sub Sample (After).

A new sub sample is created after the current sub sample, and its details window opens as shown in the figure below.

4. Type the name for the sub sample into the Name field, and fill in the remaining details as appropriate (the Total Target must be specified) - .
5. Click Save to save the new sub sample.

Note: You can also select Duplicate from the right-click menu to make a copy of the currently selected Sub Sample and its underlying Group Sets.

Figure 3 - Example of a sub sample editor page

Adding Custom Code

You can define one or more variables for which you can specify values in the Sub-Sample and Group levels. When you add a custom code, it appears in the sub-sample / group window with the name you have given it. If you add values to both the Sub-Sample and Group levels, then the Group level takes precedence.

To add a Custom Code:

1. In the Sub Samples Editor page, click the Add Row button for the Custom Code field.

A new row is added to the Custom Code list.

2. Type a name for the code into the Name field.

Note that the name must include only alpha-numeric characters - no special characters or space.

3. Click Save.

The new Custom Code will now appear in the Sub Sample Editor page.

Global Custom Code

You can define a variable and a value that will be given to all panelists who are selected for the sample file.

Type in the name for the global code and give it a value. If you wish to add more codes, click the Add Row button.