====== Random Selection for Questionnaires ======

Multiple questionnaires can be created in one survey project (**Compose Questionnaire** -> //Further questionnaires// tab). If the participant calls up the [[:en:survey:url|URL to the Questionnaire]], it can be randomly assigned to one of the questionnaires. There are options explained at the bottom in **Compose Questionnaire** -> //Further questionnaires// tab -> //Random Selection for Questionnaires// which can be selected in order to achieve this.


**Note:** Random selection of questionnaires has some restrictions (see notes below) and this option is __only__ sensible __in a few__ exceptional cases. As a rule, it makes much more sense to use normal [[randomization|randomization]].

===== Notes =====

Selection or random selection takes place every time the project folder is selected without a specific questionnaire being specified ([[:en:survey:url]]). This address (URL) is found under **Survey Project** -> **Project Settings** -> //Project folder//. 

In an unrestricted random selection, the different conditions will usually usually drawn an unequal (!) number of times. If 100 people are spread across 5 groups, the groups could be distributed as follows: 32, 7, 13, 28, 20. The larger the subgroups, the more unlikely (not impossible!) there will be disproportional variations. If groups of the same size are required, a [[random_urns|randomization with urns]] within a questionnaire is the method of choice.

The same goes for a weighted random selection: as a rule, approximation to the desired distribution only occurs in the region of larger numbers (n > 1000). Statistical outliers are therefore not possible either. 

The questionnaire a participant fills in is always noted in the variable ''QUESTNNR'' ([[:en:results:variables]]) in the data record. This applies to the explicit selection of the questionnaire in the link, just like the random selection of a questionnaire.


===== Set Questionnaire as Default =====

One of the questionnaires will be used as default if this option is chosen. The link to the survey project will then always lead to the same questionnaire - except when another questionnaire is explicitly specified in the link.


If only one questionnaires exists in the survey project then this questionnaire will always be used as default.


===== Random Selection from Selected Questionnaires =====

One or more questionnaires can be selected with this option. If the URL is called up without a questionnaire being specified (see above), this means one of the selected questionnaires will be chosen at random. 

**Note:** As a rule, an unrestricted random selection results in questionnaires being called up different numbers of times. Therefore, please take the information above into consideration. 


===== Weighted Random Selection =====

Weighted random selection represents an extension of a random selection. The principle is the same as a random selection: one of the questionnaires from those with specified weighting (i.e. not 0) will be selected at random.

Questionnaires with a higher weighting are therefore chosen with a correspondingly higher probability. The specific numbers that are input is not important, what matters is the relation: a questionnaire with a weighting of 2 will be (for example) selected twice as often as one with a weighting of 1. A questionnaire with a weighting off 66 will be selected twice as often as a questionnaire with a weighting of 33.

