Combining radio and checkboxes [duplicate]

Question

This might be a technical question or maybe there's a better way of approaching the area but what is the best interaction for asking users to select either an unknown or the specific items.

Answer 1

"asking users to select either an unknown or the specific items". If I understood correctly the case, you can be literal with the question you want to ask:

^{download bmml source – Wireframes created with Balsamiq Mockups}

Answer 2

I think what you describe is similar to "None of the above". If by "Either" you mean the user selection of something in the form is mandatory, I would be fine with something like the following, where selecting the last option deselects everything above it. From what i've seen and implemented, this feels natural and even appears often in governmental paper forms.

^{download bmml source – Wireframes created with Balsamiq Mockups}

However, without knowing your use case better, I can't help but think that if the user has Item 1 but the second item is of unknown type, there is no option in that form that satisfies the user's needs.

Answer 3

You might found anwer in this post : Using mixed radio and checkbox buttons - is there any efficiency or usability gain in the design? with Design B recommendation. Two step form can improve comprehension.