If...Then...Else is a flexible way of defining conditional statements. It can be used with expressions of any complexity, based on the answers to one or more questions.

Suppose the metadata section defines the following questions:

All respondents should be asked the Color question, followed by the questions related to the colors that they say are suitable for the product. So, for example, respondents who think that red and yellow and yellow and green are suitable colors will see the Red and the Green questions, whereas respondents who say that none of the colors is suitable will see no extra questions at all. You specify this in the routing section as follows:

If a respondent fails an If test of this type, they continue with the next statement in the routing section. Sometimes, though, you'll want to specify some other action for these respondents. In these cases, you need to include an Else section with the If:

In the following example, anyone who mentions red and yellow packaging at the Color question is asked why they think it is a good color for the product. Anyone who does not mention it is asked why they did not choose it:

Not all conditional actions are based on simple either–or tests; many will consist of a number of tests each for different responses. In this situation, you extend the basic If...Then..Else statement to include ElseIf clauses:

You may write as many Else...If clauses as you need. Each respondent passes through the whole If...End If group of statements from top to bottom until one of the expressions returns True. At this point the actions for that expression take place and then the respondent continues with the statement immediately after End If. It is therefore important that the expressions are mutually exclusive — that is to say, only one expression must be True for each respondent. If the expressions are not mutually exclusive and a respondent can pass more than one test, the actions for the first test will be always carried out, and the second test will never be reached.

Here is a variation of the first example that combines the three separate If statements into a single group. The question has been changed from multiple choice to single choice to ensure that each respondent satisfies one expression only. The Color question is now:

The If statement that asks the color-specific questions can be written as follows:

Respondents who think that none of the color schemes is suitable fail all three tests and do not see any additional questions.

If clauses may contain other If clauses. This is called nesting. What this means in practise is that you can accumulate characteristics on an incremental basis, each time reducing the number of respondents eligible to answer the next question. In the following example, we want to ask different questions depending on whether or not the respondent usually travels to work by train. We also want to ask this group of respondents different questions according to their general opinion of the train service. The questions are defined in the metadata section as follows. They are listed in the order they are used in the routing section, but this is not a requirement.

The routing statements that implement the questionnaire logic are as follows. The comments explain who sees each question, and the indentation highlights the relationship between the various sections of the code.

To illustrate how this example works, suppose we have three people:

When you write nested loops of this type, be careful that you structure the If and Else clauses correctly; otherwise, your script may not do exactly what you expect. Indenting all the statements in each clause by the same amount helps. Make sure that each If has an End If. However, if you find that the logic is becoming difficult to follow, try breaking the block into a number of separate, unnested blocks, and see whether that makes the script easier to work with.