Often, researchers want equal numbers of participants to do different conditions, or do the same conditions in a different order.

This lesson shows you how to do this in PsyToolkit with two different examples.

Showing half participants different information

In this example, all participants will be asked how good they feel, but exactly half the participants get a positive and the other a negative "prime".

Let’s say we want 10 participants in both conditions. In the edit survey screen, for counterbalancing, you enter 10 10 as shown in the image below.


You will see that once you entered this, you will automatically have a maximum of 20 participants.

This will mean you get to "groups" with each 10 participants. In PsyToolkit, you can use the label psy_group to determine which group a participant will be in. Because there are in total two groups, the value of psy_group will be either 1 or 2. You can then use this value to let people see different messages, do different experiments, and so on.

l: decide_what_people_get
t: jump
- if $psy_group = 1 then goto positive_message
- if $psy_group = 2 then goto negative_message

l: negative_message
t: info
q: Today, it will be raining and it is windy, so you cannot use an umbrella

j: feeling_question

l: positve_message
t: info
q: Today, it will be sunny and pleasant outside.

l: feeling_question
t: radio
q: How happy are you today?
- Very happy, it is going to be a great day
- Moderate, I a bit concerned about the weather
- Unhappy, I think it is going to be bad weather

Different groups do different experiments or none at all

Different participants do Stroop experiments (20 participants), some do Simon experiment (20 participants), and only 10 do no experiment at all.

For this, in the counterbalancing line enter 20 20 10. Group 1 (20 participants) will do Stroop, Group 2 (20 participants) will do the Simon task, and 10 will do no task.

l: decide_what_people_get
t: jump
- if $psy_group = 1 then goto stroop_experiment
- if $psy_group = 2 then goto simon_experiment

l: stroop_experiment
t: experiment
- stroop

j: final_question

l: simon_experiment
t: experiment
- simon

l: final_question
t: radio
q: Were you concentrating in this survey?
- Yes
- No