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--- en:create:functions:random [10.04.2016 10:20] – [Drawing with Replacement] admin
+++ en:create:functions:random [06.06.2017 13:30] – admin
@@ Line 8: / Line 8: @@
   * //max//\\ The largest number allowed
-**Note:** If a random draw without replacement is used in an experiment, then different sizes of experimental groups are inevitable. SoSci Survey offers [[:en:create:random_urns|urns]] for random draws with replacement.
+**Note:** Although one could create an experimental randomization via ''random()'', we strongly recommend using a [[:en:create:questions:random]]. For more information abour randomization an experimental groups see [[:en:create:randomization]].
-**Note:** See [[:en:create:randomization]] for the application of random draws.
@@ Line 18: / Line 16: @@
 //min// ≤ return value ≤ //max//
-==== Drawing with Replacement ====
-The PHP functions ''[[:en:create:functions:random|random()]]'' and ''[[:en:create:functions:random_p|random_p()]]'' (for weighted random draws) randomly draw with replacement. An unrestricted random draw "with replacement" is comparable to throwing a die. As a rule, group sizes vary greatly here and this can be problematic for the analysis.
-**Note:** When drawing with replacement, it is crucial to ensure that the random number is saved in the data record. To do this, use an [[:en:create:questions:internal|internal variable]] and the function ''[[:en:create:functions:put|put()]]''.
-  - Add a new question in the **List of Questions** using the type "Internal Variables" (e.g. with ID ''IV01'')
-  - Add a variable (item) in this question with the description, as an example, "random number". According to the **Variables List**, this variable's ID is ''IV01_01''.
-  - [[:en:create:php|PHP code]] is used to carry out the actual random draw.
-<code php>
-$number = random(1,4);  // rolls a number between 1 and 4
-put('IV01_01', $number);  // saves the number in IV01_01
-</code>
-===== Example =====
-In the following example, a number between 1 and 3 is drawn and the participant is shown one of the text elements "stimulus1" to "stimulus3" corresponding to the number. The function ''[[:en:create:functions:put|put()]]'' is used to save the drawn number in the data record.
-<code php>
-// Draw a random number
-$stim = random(1, 3);
-// Save the result of the draw in the data record
-put('IV01_01', $stim);
-// Display stimulus
-if ($version == 1) {
-  text('stimulus1');
-} elseif ($version == 2) {
-  text('stimulus2');
-} else {
-  text('stimulus3');
-}
-</code>