A clinical psychologist wants to investigate whether a new digital mindfulness app reduces state anxiety levels compared to a standard guided-breathing worksheet.

To test this, they recruit 48 participants who report high daily stress levels. Participants are randomly allocated to one of two groups:

• Group Alpha: There are 24 participants in this group. Each participant is placed individually in a quiet room and given 10 minutes to use the interactive digital mindfulness app on a tablet, after which they complete a standardised state anxiety questionnaire.
• Group Beta: There are 24 participants in this group. Each participant is placed individually in a quiet room and given 10 minutes to read and follow a standard printed guided-breathing worksheet, after which they complete the identical standardised state anxiety questionnaire.

Identify the experimental design used in this study and outline one advantage of this experimental design.

Table 1: Total state anxiety scores across both groups