====== Obtaining the Participant's Consent ======

There are a number of cases in which the participant's consent must be obtained, for example for informed, voluntary participation in an experiment (i.e. the principle of "informed consent") or if you wish to store and process the participant's personal data.

For the consent to be effective, the participant must actively agree. A phrase "by participating, you agree with ..." is therefore usually __not__ sufficient.
 
===== Integrate Information Texts =====

As a rule, you first need to tell the participant what he or she agrees to. There are different ways to do this: 

  * Display an according message directly as content/a page in the questionnaire ([[en:create:texts]])
  * Open a new window when the participant clicks on a link (''[[:en:create:functions:textlink]]'') or show further explanations when a button or text is clicked ([[:en:create:popup]])
  * Link to a PDF document with further information ([[:en:create:media]])

If you display the text directly on a questionnaire page, the participant is initially confronted with a lot of text - but this is the only option that ensures that the information is really displayed. 

Optionally, it is possible to display the necessary information at the top of the page, then use ''[[:en:create:functions:buttoncode]]'' to display the "Next" button (optionally with different text, see below) and provide further details (e.g. complete data protection information) below.

**Tip:** Do not place the information text on the first page of the questionnaire, but on the second. Use the first page for a friendly, concise welcome to the questionnaire. Then the participant is not immediately overwhelmed by the (usually long) information text.


===== Option 1: Check Box =====

When giving their consent of participation, participants usually must tick a selection box. To do this, create a new question of the type "Multiple selection" with the option "I would like to voluntarily participate in this study". The wording should of course fit the purpose in question. 

**Tip:** If the participant has to agree to several things (e.g. participation and storage of personal data), you can create two such questions or insert two options in the question. 

You have several options for checking that the field has actually been selected: 

==== 1. Discharge the participant from the survey with the possibility to return (recommended) ====

To do this, you first need a text that should be displayed if the participant does not select the box and clicks "Next". Create this text in the list of questions in a category with **add text**.
 
Then, under **Compose Questionnaire**, select the page __after__ the consent question. Insert an element of "PHP-Code" at the very top. The following example code assumes that the consent question has the identifier "EW01" and the text has the identifier "EW02".

<code php>
// If the option EW01_01 was not selected ...
if (value('EW01_01') != 2) {
  // …show the text
  text('EW02');
  // Display a "back" button, no "next" button
  option('backbutton', true);
  option('nextbutton', false);
  // Do not display anything else on this page
  pageStop();
}
</code>

==== 2. Discharge the Participant without the Possibility to Return ====

Create a text in the **list of questions** that is to be displayed when the participant clicks on "Next" without having selected the option for consent. 

In the consent question under //filter question//, select the option "If the following options are __not__ all marked..." and select the option for consent. For //filtering//, select "End interview (screenout)", and here select the text that you must create in the question catalog in advance. 

**Disadvantage:** If the participant accidentally overlooks the consent check box, the interview is over.

==== 3. Prevent Continuation of the Interview ====

In the **list of questions**, create a __short__ text that is to be displayed at the top of the page as a note if you have not checked the box for consent. 

Under **Compose Questionnaire**, select the page after the consent question. Create an [[:en:create:checks#individuelle_antwort-pruefung|individual answer check]] here. To do this, drag an element "PHP code" at the top of the page. The following example code assumes that the consent question has the identifier EW01 and the note text has the identifier EW02.

<code php>
if (value('EW01_01') != 2) {
  markFail('EW01');
  repeatPage('EW02');
}
</code>

**Disadvantage:** In the context of sensitive experiments, one could accuse you that the participants are urged to give their consent.

==== 4. Prevent Continuation of the Interview (simplified) ====

In the question, under //checking the answer//, set the following: 1 //Options must at least be checked//.
 
**Disadvantage:** The error message displayed if the cross is missing does not match the problem.
 
**Disadvantage:** Here the participant is clearly urged to check the box.


===== Option 2: Explicit "No" Option =====

If you offer a negative option in addition to the positive response option (consent), you can avoid two pitfalls: 

  * The participant cannot accidentally overlook the question
  * The participant is not urged to check the (only available) option

You need a text to be displayed if the participant does not want to participate in the study. Create it in the **list of questions** in a category with **add text**. 

Then create a question of the type "Selection" in the **list of questions**. Enter two selection options. Sometimes it is recommended to offer the negative variant first:
 
  * "No, I don't want to participate in this study"
  * "Yes, I would like to participate in this study"

Under //Selection Options// for //Completeness Check//, select that the question needs to be answered. 

After saving the question, under //Filter question// under the condition "If one of the following options was selected...", select the "No" option. For //filtering//, select "End interview (screenout)" and select the text that you have created above. 

Under **Compose Questionnaire**, drag this question under the information text to one of the first pages in the questionnaire. 

**Tip:** For the consent question, select the //display variant// "Card" for the //display options//, display it in 2 columns (//several columns//) if necessary. With //Automatic "Next"//, you can specify that the questionnaire continues directly after the click. If you also hide the "Next" button, the participant cannot leave the question unanswered. 

**Tip:** If you want to optimize the note that is displayed when the participant does not select any of the options (see tip above), use an [[:en:create:checks#individuelle_antwort-pruefung|individual answer check]].


===== Option 3: Consent at the Push of a Button =====

The labeling of the "Next" button can be adapted as required. Instead of "Next", it can be labeled "I would like to participate voluntarily in this study". The text must of course be adapted according to the type of consent. 

To do this, add an element of "PHP code" to the page with the information text under **Compose Questionnaire** and enter the following code: 

    option('nextbutton','I want to voluntarily participate in this study'); 

**Disadvantage:** With this option you run the risk that the participant does not consciously agree, but simply searches for a button to start filling in the form.