# Radio Buttons vs Dropdown in a Form A/B Test

Page: https://alidemirbas.com.tr/en/lab/ab-test-library/tests/radio-buttons-vs-dropdown-in-a-form-ab-test

## Hypothesis

Radio buttons show every option up front, so users can compare and choose without an extra tap, while a dropdown saves space and can make the form look shorter. If seeing the options eases the decision, radio buttons may bring a higher form completion rate; if a shorter-looking form matters more, the dropdown may come out ahead.

## When to run this test

Long pauses at a single-select field in field analytics, validation errors from missing selections, or session recordings of visitors opening and closing the dropdown mark that field as a sticking point. With the right format, users get through the field faster and fewer abandon the form there. If the option set is so short or so long that one control is clearly a poor fit, use the control that suits the context instead. If you do test, start both arms with nothing selected and give the dropdown an empty "Select an option" entry, so the first option is not chosen by default.

## Primary metric

**Form completion rate**: Compare successful submissions to see whether the selection format affects completion.

## Other metrics

- **Field completion time**: Measure time from first interaction with the field to a valid selection.
- **Field-level abandonment**: Compare visitors who reach the selection field but leave before completing the form.
- **Invalid selection rate**: Track invalid or missing choices; changing a valid preference is not an error.

## What to check before and during the test

- **Format**: Compare the same option set as radio buttons and as a dropdown.
- **Keep constant**: Keep options, order, default selection and validation unchanged.
- **Completion**: Read completion of the field alongside form completion.
- **Errors**: Separate changed selections from validation errors.
- **Keyboard and accessibility**: Check keyboard navigation, screen-reader announcements and mobile usability for both formats.

## What to watch when reading the result

- A shorter field completion time does not pick the winner by itself; the form completion rate does. Count only invalid or missing choices in the invalid selection rate, and do not read a user changing a valid preference as an error.
- This comparison tells you only about the field and option set you tested; rerun it in another single-select field before applying it there. Review mobile and desktop separately, and make sure mobile keeps the platform's native dropdown and that keyboard and screen-reader behavior stays intact for both controls.
- A small or unclear difference does not prove that the two controls work equally well. Enter the smallest difference you care about and the current form completion rate in the [sample size calculator](https://alidemirbas.com.tr/en/calculators/sample-size-calculator), and compare the sample it gives per variant with what the test collected. If the test fell short of it, the difference may simply have gone undetected; then accessibility and space needs may decide the choice.

## Frequently Asked Questions

### How should option count guide radio buttons versus a dropdown?

Few short options may benefit from being visible together. Longer lists can suit a dropdown. There is no universal count cutoff. Consider task, labels, defaults and device, then test usable controls with the same options.

### Should changing a selection count as an error?

No. A valid preference change is not a validation failure. Track invalid or missing choices separately from ordinary changes.

### Can a preselected dropdown option create a problem?

Match the initial state between arms. If starting unselected, include an empty “Select an option” entry; otherwise a native select may initially choose the first item. Do not inflate completion through unnoticed defaults.