Can we use Radio/Checkbox for mandatory form fields

Question

I am working on designing a website which has admin side fuctionalities involving large number of forms related to creation of sevaral entities within the application along with normal user login. The requirement says there should be an error if mandatory fields are missed while saving the form.

eg. The field Frequency has 3 values to choose from - Daily, Weekly and Monthly.

Option 1

Using a mandatory select input which would have the default value "select" and show and error if not filled on saving the form. Here 2 clicks are required to select a desired option.

Option 2

Using a radio button and having it defaulted to one of the options (NN/g 's article Radio Buttons: Select One by Default or Leave All Unselected? concludes saying always try to Select One Radio Button by Default). Here, if this field is missed while filling the form no mandatory field error message would be shown.

Which option would be the correct approach? Is there any alternative solution?

Answer 1

TL;DR:
Overview: With only 3 options, radio buttons are better than dropdowns in terms of overview.

Pre-selected default: Is one option predominantly desired by the users? Then do it.
Is the choice here really important and all 3 choices are equally desireable? Then don't do it.
Or keep the dropdown instead so it doesn't violate the radio button guidelines.

---

Usually, if the amount of options for a selection is overseeable, radio buttons are better
(see this similar question for reference: Radio buttons or Dropdown for same list of options)

But precise UX advice is mostly always context dependant. This question here Dropdown vs radio button provides some very insightful answers. Basically, radio buttons better emphasize the other options and make it easier to choose.

And as you and other sources (Should radio buttons be pre-selected?) pointed out, one default option is mostly always desired to be selected.
But that is to make life easier for the user. As your referenced NN-Group article points out

When a choice in a set of radio buttons is known to be the most desired or frequently selected one, it is very helpful to select this by default in the design.

So you should ask yourself, is there one option of these 3 that is the dominant one? The one that about 60-80% of all users choose. If that is so, it would make sense.

But if all 3 are equally desireable, and if the decision has a great impact on the result, the user should be able to carefully choose between the options. Isn't the point of mandatory items to really point it out to the user? If the choice is so important but you already select one, it might make the system very error prone in the eyes of the user.

So you have to really take the context of your application into account and carefully decide what would be the best for the user.

Answer 2

If you have this few options it is always better to show them as radios. This way the user sees what options there are in one blink of an eye. In a select, a user does not know what to expect before he clicks.

Select dropdowns: long lists where other options don't matter (countries e.g.).

Radios: short list where the other options are also important (preferred option e.g.). TIP: you should put the radio options in a column instead of a row (better and quicker readability).

About the pre-select: this comes down to how important correct data is to the system. Pre-selected means that the user can read over it without noticing it (and thus leaving it to default). If you want to be sure the information sent by the user is correct and complete you should let the radios be initially unselected.

Answer 3

Radio button with a *(mandatory field indication) & with no pre-selected values.

Answer 4

Using drop-down will hide out options from the user. In addition to this, an extra click is required.

I would prefer using a radio button instead of a checkbox. Reason being it doesn't hide options & no extra click is required from the user. Radio button with no pre-selected value.

By adding "*" user will get to know this is a mandatory field.