I want to develop a questionnaire. Because the target population are children, I used 3-point likert-type scale (0 1 2) for my items. Now I want to remove invariant items (i.e. the items not having enough variance). Are there any standards for determining minimum variance value according to different likert-type scales? The issue could also be viewed from a frequency point of view. Is there any specific portion of people (e.g. 80% of them) that if they respond to an item identically (e.g. all responded 0) the item should be regarded as invariant?