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Question Scales Part 2: Should I allow for “N/A” or “I don’t Know” in my response options?

In the previous post we talked about using an even number of items in your response scales to remove any “neutral” response – so now let’s talk about the other types of “non-response response” – the (very very careful) use of “N/A” (“Not Applicable”) or “I Don’t Know”.

Start with opinion vs fact

I won’t go into great detail as to whether any given survey question addresses opinion or fact as I’ve covered that in  Question Scales Part 1: Should I use an even or odd number of response options?, but clearly this is where you start, as “I Don’t Know” doesn’t make any sense on a question about opinion.  (I don’t know my opinion? You might not have one, but that is something else and we’ll cover that below.)

What it’s all about. Getting good data while avoiding an “easy out” 

There are absolutely valid reasons to allow for “N/A” or “I Don’t Know” as question options, but there are also some absolutely terrible ones that might cause a respondent to choose these incorrectly.

Good uses of “N/A” or “I Don’t Know” as a response (by the respondent)

  1. This is not applicable to me. If you think this might actually be a valid response, either:
    1. explain what you mean by this response inside the question text. Ex.  “If you don’t have contact with senior management, please indicate N/A“.
    2. or better, use a filter question. Ex. “Are you in contact with senior management as part of your job?” (Yes/No), then follow with, “If Yes, please answer the following:
  2. I don’t know the answer. (regarding “fact” questions) If this is truly possible then:
    1. it would clearly be ok to add a “Don’t Know” option.
    2. or as above, it would be better to add a filter question beforehand that takes care of this before the question is addressed.

Suboptimal uses of “N/A” or “I Don’t Know”

(by the respondent)

  1. I don’t know how I feel about this one way or the other. (On opinion.) As mentioned above and in the previous post regarding “forced choice” this is almost never truly the case, and so just becomes an easy out … as opposed to …
  2. I don’t care, or I don’t want to think about it too much as I want to get this survey done ASAP. 
  3. I don’t understand what you’re talking about. “I Don’t Know” may become the only only rational option when the question is not worded well, or they don’t have enough information to answer.  In either case this is clearly a terrible reason to include “I Don’t Know” as a response, and it’s obviously better to fix the question or provide the info needed beforehand.

To recap

  1. If questions are well-worded and accompanied by appropriate filter questions, “N/A” and “I Don’t Know” are almost never needed and should not be included in your response options.
  2.  If you DO use “N/A” because a filter question is just not viable, use it very sparingly.
  3. I Don’t Know” should only be used in regard to fact-based questions.

Hope this was of help, but as always give us a shout if you would like to discuss!

Next up Question Scales Part 3: How many response options should I have, and what is a Just Noticeable Difference? (JND)

Thanks for reading, and if you’re interested in discussing a survey for your organization call us at 1-604-219-7876, email us at, or just book a discovery call for a one-on-one chat.

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Adam Hunter has a Bachelors degree in Mechanical Engineering, an MBA, and 35+ years of technical and programming experience, resulting in a broad mix of analytical, statistical, project-related and business skills. (Linkedin)