Trial block

A study may contain one of more trial blocks (or zero if it's a simple questionnaire). A trial block is home to a set of constructs, in running order. You can only create trials within a trial block.

Creating a trial block

Trial blocks can be added to the study sequence. Click New item, select Trial block from the type list and select one of the following creation options:

  • New: create a new trial block.
  • Copy: copy another trial block from the current study.

Adding a construct

You can add constructs to the trial block by clicking on New item or by dragging a compatible construct from somewhere in the study tree into the trial block. When creating a new construct, you can choose to start with a blank slate or to copy an existing construct from the study.

Removing a construct

Constructs can be removed from the trial-block by dragging them to somewhere else in the study tree, or by selecting the construct using the checkbox and clicking Delete in the toolbar above the trial-block table. You can also select and delete multiple constructs at once.

WARNING: All sub-constructs of the selected constructs will also be removed. If you wish keep any sub-constructs, you can drag them to another part of the study tree. Alternatively, you can drag any construct to the Spare parts bin to remove it (and its sub-constructs) from the study without permanently deleting it.

Navigate to a construct

You can navigate to any of the constructs in the table by clicking on its row or by clicking on the construct in the study tree.

Reordering constructs

The order of constructs can be changed by dragging and dropping within the table in the view panel, or by dragging and dropping within the study tree.

Assigning participant groups

One or more participant groups can be assigned to a trial block by selecting them from the Participant groups list and clicking Save. Setting the number of groups in the study can be done at the root of the study tree (Figure 1).

Counterbalancing trial blocks

Trial blocks can be grouped at the root of the study tree (Figure 1) for the purposes of counterbalancing.

Figure 1. Study tree root

Figure 1. Study tree root

To counterbalance trial blocks, we first need to create a block group by clicking Add block group in the Counterbalance trial blocks table (Figure 2).

Figure 2. Counterbalance trial blocks

Figure 2. Counterbalance trial blocks

Click Add block to add individual trial blocks to the group.

Select a counterbalancing strategy from the Strategy list and set the number of cycles (if applicable) using Cycles. The following counterbalancing strategies are available:

  • Random order: Randomize the order of execution of blocks in the block group. Only available when block group contains at least two blocks.
  • Block randomization: Block randomization is a subject-by-subject counterbalancing method to control non-linear progressive error in within-subjects designs. For example, given blocks ABC and cycles set to 4, block randomization might produce BCA-CBA-ACB-BAC. Only available on contiguous blocks when block group contains at least two blocks. Blocks in this group must be contiguous in the study tree.
  • Reverse counterbalance: Reverse counterbalance is a subject-by-subject counterbalancing method to control linear progressive error in within-subjects designs. For example, given blocks ABC, reverse counterbalance will produce ABCCBA. Only available on contiguous blocks when block group contains at least two blocks. Blocks in this group must be contiguous in the study tree.