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How do I balance my sample within demographics?

You may wish to receive a specific distribution of participants across selected demographics. For example, if you want a 50/50 split of male and female participants, or to recruit 30% of your participants from Spain and the rest from France.

Our 'Balance sample' feature allows you to distribute your study to an equal number of male and female participants. Alternatively, you can balance your sample across other demographics by running multiple duplicate studies. Read on to find out more!

Balance sample across sex

In the Audience section of your study form, tick the Sex checkbox to enable the 'Balance sample' feature. This will distribute your study equally to selected options on the Sex pre-screener.


By default, enabling this feature will balance your sample to 50% male and 50% female participants.

To toggle the balance of your sample, simply choose 'Manage options' when the feature is enabled and select the options you wish to target for your study.

You can apply any additional prescreening that you need on top of balancing your sample. The number of matching participants will update to account for the sample balance.

Additional information

The Sex pre-screening question is phrased as 'What sex were you assigned at birth, such as on an original birth certificate?' Participants answer this question with one of three options: [Male / Female / Rather not say]. Studies are balanced across the first two of these options only, using the Sex data provided by participants

Balance sample across any demographic

For any demographic where you want a specific distribution, you can run multiple studies which point to the same study URL.

First, set up your basic study with all of the necessary details and save it as a draft. Then duplicate it via the action menu, giving you two identical studies.

On one of these studies, you should add prescreening criteria to target one of your desired demographic groups (e.g. Nationality = Spain). On the other, your prescreening should target a different demographic group (e.g. Nationality = France). You can duplicate your study several times if you wish to balance across more than two groups.

In this way, you can target the exact number of participants you require in each demographic group. You can link these duplicate Prolific studies to the same Study URL, and use the same completion URL to return participants to Prolific.

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