Running focus group pre-tasks online, using software designed for that purpose, has several advantages over other methods of running pre-tasks. Here are some of the main ones.
It allows you to easily monitor levels of compliance by viewing the activity of each participant throughout the period of task. This helps to reduce the risk of a participant turning up to one of your groups having failed to do what you asked them to do.
Warming up participants
You can allow participants to communicate with each other during the pre-task, so that they can start to get to know each other before meeting face to face. This can help to break the ice more quickly when they meet.
Different pre-tasks for different participants
In theory you could achieve this even if you did not run your pre-tasks online. However, it would be very difficult. By running your pre-tasks online you can easily have some participants doing some tasks, and others doing different tasks. And you can change these as you are going along.
You can engage with your participants during the tasks, in response to the posts that they make. For example, you can ask them to elaborate on or explain a post, or just give encouragement or thanks.
More varied pre-tasks
You can ask your participants to do a variety of tasks that would not be possible offline. For example, some may be written posts, but they could also be images or videos, or links to particular pages on websites. Apart from anything else, this can all help with engagement levels.