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Conditions for multiple choice questions -- How to make sure they express what you want

Posted on 3/19/2011 by Jim in category: survey software tips
Novi Survey online survey software allows formulating sophisticated conditions in page conditions, skip logic, alert conditions, and report filters. Conditions are logic elements (more specifically predicates) of the form:

Atomic Question data element –  Operator  –  Value

While available question data elements in the survey tool depend on each question type, they can be thought of as individual clicks or piece of text or data from a participant. For example, the choice of an answer in multiple choice questions is a question data element. For an open ended question of type date with three fields, each field corresponds to a question data element. Each checkbox in a matrix of checkboxes is also a question data element.

Given a response to a survey, a condition will evaluate to either “true” or “false”. It may then be combined with other conditions as constructed in the page condition, alter, report filter, etc.

A common misunderstanding on how to formulate conditions arises when used for multiple choice questions.
Here is an example of a multiple choice question where a single selection is allowed:

Q1 -- Which food would you rather have among those listed below?

1)  Peanut butter and crackers
2)  Potato chips
3)  Blackberries
4)  Roasted chicken
5)  Smoked salmon

Now, consider condition:

Q1 is “Potato chips, Peanut butter and crackers”

Can Q1 ever be “Potato chips, Peanut butter and crackers”? The question allows selecting only 1 choice so the response to Q1 can be “Potato chips”, it can be “Peanut butter and crackers”, but it can never be both. Therefore, the condition as formulated can never be true. A condition that will always evaluate to either true or to false for every response is never useful.

The intent for formulating conditions as shown above is typically to have the condition be true if either of the choices is selected. The asp survey tool supports this type of condition through operator “is a subset of”. Reformulating the condition with the correct operator yields:

Q1 “is a subset of” “Potato chips, Peanut butter and crackers”

A shown above the condition will be true if (and only if) the response to Q1 is “Potato chips” or “Peanut butter and crackers”.

Novi Survey tool will validate for conditions that will always evaluate to either true of false through the validation tool in the survey list. When the validation detects conditions that will be always (or never) true, you should go back to the logic constructs containing the condition and modify them.

Happy surveying with Novi Survey online survey software

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