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Basic survey logic

Reference Number: AA-00339 Last Updated: 2014-07-16 22:32

Survey logic is designed so that a survey flows in a coherent manner. It allows the answer of one question to determine subsequent questions. Any time you would write something such as "If you answered 'X' in the previous question..." you should use branch or skip logic.

The Golden Rule

Every question in the survey will be asked sequentially, unless you define logic which dictates otherwise.

Two basic forms of logic are skip rules (also called pre-requisites) and branch rules. 

  • Skip rules allow certain questions or sections to be skipped if they do not apply to a certain respondent. 
  • Branch rules route a respondent to the part of the survey that is relevant to him, based on a given response. 

These concepts are illustrated in the picture below:

This article outlines:

Once you are comfortable with these concepts, you can explore advanced survey design concepts.

Skip rules (pre-requisites)

Skip rules are useful when you would like to skip questions or sections in your survey that do not apply based on logic you define.  Question or section level pre-requites will allow one question or an entire section to be skipped, based on the criteria that you specify. For example, you might want a respondent who answers that they are male, to skip a question about pregnancy, or to skip a whole section of questions about experiences during pregnancy.

This section explains:

How do skip rules (pre-requisites) work?

Skip rules configured for a question or section are evaluated before the question or section is displayed during survey conduction. Skip rules can be applied to any type of question.

A skip rule consists of:

  1. A source question (numeric or option-type only)
  2. A condition which - if true - will cause the question or section to be skipped

In the example described earlier, the source question would be the question which asked the gender of the respondent, and the condition would be when “male” was selected as the response to this question.

If the source question is a single select question:

  • Operators = and ≠ are permitted.
  • Value of condition must be one of the source question’s configured options.

If the source question is a multiple select question:

  • Operators INCLUDES and EXCLUDES are permitted.
  • Value of condition must be one of the source question’s configured options.

If the source question is a numeric question:

  • Operators =, ≠, > and < are permitted.
  • Value of condition can be any number.

If the configured condition is evaluated as true, the question or section that it is configured for will be skipped. Otherwise, it will be displayed.

Multiple skip rules may be configured for a question or section. Rules may be configured such that the question is skipped as soon as any of the rules evaluate to true or such that the question is skipped only of all the rules evaluate to true.

In the example below (Figure 1), the question 1.12 will be skipped if the source question,  "Household Source of livelihood (1.11)" had a response equal to "No source of income [8]".

Figure 1:

In the example below (Figure 2), the question 6.35 will be skipped if the response to the source question, "Who would you prefer to test you (6.34)" excluded value: Other [3].

Figure 2:

In the example below (Figure 3), section 2 will be skipped if the response to the source question: Gender (1.1) equals: Male [1].

Figure 3:

Creating a skip rule

To configure a skip rule:

  1. Select the Design tab. 
  2. Click on the name of the question/section you would like to be skipped (see Figure 4). 
  3. Select  "Add prerequisite" from the dropdown menu. 
  4. A dialog box will load (see Figure 5). Create the pre-requisite(s) as needed.
  5. If you apply multiple pre-requisites to a question, select whether the question should be skipped if any of the pre-requisites are met or all of them must be met. 
  6. In the example shown in Figure 6, question 1.4 (Avg Income) is skipped only if the answers to both 1.2 and 1.3 are 'No'. 

"AND" vs "OR" pre-requisite support

The ability for a question to be skipped if any of the rules are met is supported across all versions of the Mobenzi mobile application. As of version 4.13.1+ of the Mobenzi mobile application, you may also specify that all of the pre-requisites must be met before the question is skipped. 

Figure 4:

Figure 5:

Figure 6:

Branch rules

Branching creates a similar result to skip logic, however, branching logic will be evaluated after the question is asked. If the condition specified in the branching logic is true, the survey will skip to the question specified. Branch rules may only be configured for numeric or option-type questions.

This section outlines:

How does branching work?

A branch rule consists of:

  • A condition
  • A destination question to branch to if the condition is met

The condition is simply the combination of a valid operator and value based on the question type. If the configured condition evaluates to true, the survey branches to the destination question, which may be any other question in the survey. If the destination question has pre-requisites, they are evaluated as normal. 

Multiple branch rules may be configured for a question.  The rules are evaluated in order until one evaluates to true and then no further rules are evaluated.

Branch rules are evaluated only once the constraints configured for the question (if any) are met.

Creating branch logic

To create branching logic:

  1. Select the Design tab. 
  2. Click on the name of the question that will create a branch to access its menu with actions specific to that section (see Figure 1).   
  3. Select "Manage Branches" from the dropdown menu. 

Figure 1:

The Manage Question Branches dialog box will load with three fields (see Figure 2):

  • 'If response to this question' - this determines whether the response you're evaluating should be equal to, not equal to, less than, greater than, include or exclude a certain value. The operators loaded in this dropdown list will be determined by the type of question that is being evaluated. If a single select question (Option List - Single Selection) is being evaluated, for example, the operators that will be available will be = (is equal to) and != (not equal to). 
  • 'Value' - this contains a list of the options available for the question being evaluated. 
  • 'Then skip to' - this is the question to which the survey must skip, given the above condition. 

Figure 2:

For example, a question asking the respondent if they have a chronic disease could have the following branching logic: If the response to this question: '=' Value: 'No' Then skip to: '2.5'. In other words, if the answer to question is 'No', the survey will skip the rest of the questions that are aimed those with chronic diseases. 

Deciding whether to use branch or skip logic

In many cases, the same result can be achieved using either branch or skip rules. The decision to use one or the other usually depends on:

  • The number of questions to be skipped based on a specific question.
  • Whether you wish to simply skip a question if some condition is true or go to a specific point in the survey.

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