Ali Demirbaş - Lab
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Forms & Signup

Radio Buttons vs Dropdown in a Form A/B Test

Radio buttons show all options immediately but use more vertical space.

  • Forms & signup
  • Form completion rate

Option A vs Option B

Two alternatives; neither is the incumbent.

Changed
Options
Page
Forms & signup
Difference
changed

Hypothesis

A dropdown takes less space but requires another action to inspect the choices. Compare the same options where both controls are usable, and check platform behavior separately.

How to run this test

Primary metric

Form completion rate

Compare successful submissions to see whether the selection format affects completion.

Other metrics

  • Field completion timeMeasure time from first interaction with the field to a valid selection.
  • Field-level abandonmentCompare visitors who reach the selection field but leave before completing the form.
  • Invalid selection rateTrack invalid or missing choices; changing a valid preference is not an error.

What to check before and during the test

  • FormatCompare the same option set as radio buttons and as a dropdown.
  • Keep constantKeep options, order, default selection and validation unchanged.
  • CompletionRead completion of the field alongside form completion.
  • ErrorsSeparate changed selections from validation errors.
  • Keyboard and accessibilityCheck keyboard navigation, screen-reader announcements and mobile usability for both formats.

Setup mistakes to avoid

  1. 1Do not change option count or order along with the format.
  2. 2Do not preselect a dropdown option in a way that visitors may accept without noticing.
  3. 3Do not use a dropdown for very few options or radio buttons for too many; each can be a poor fit in the wrong context.
  4. 4Do not replace a platform-native mobile dropdown with a custom control that breaks accessibility.
  5. 5Do not generalize results from one field type to all single-select fields.