[RESOLVED] Random number with statistical distribution

• 11-30-2013, 11:45 AM
wbport
[RESOLVED] Random number with statistical distribution
I need help converting a Math.random() number into something that would simulate the distribution curve. For example, if the mean were 10.0 and a standard distribution was 1.0, the returned random number would be more likely to be between 10.0-10.5 than 10.5-11.0 and something > 13 would be extremely rare.

• 12-04-2013, 08:31 AM
wbport
Got it. I ran the random function 20 times, summing the results. After tweaking the factor by running it 100,000 times, I got:
Code:

```<html><head><title>Rubato test</title> <script language="JavaScript"> function startup() {document.tournform.Compute.focus();} function playOne() {   var randSum=0;   for (var i=0; i < 20; i++)     randSum+= Math.random();   return (randSum * 0.777) - 7.77;   return r; } function calculate() {   var OutText = "";   var sum=0;   var sumSq=0;   var Min = 100000   var Max =-100000   var StdD = 0     for (var i = 0; i < 100000; i++) {     var x = playOne();     sum += x;     sumSq += x * x;     if (Min > x) Min = x;     if (Max < x) Max = x;   }   mean = sum / 100000   StdD = Math.sqrt( sumSq / 100000 - mean * mean);      OutText = "The mean is " + mean + " min value = " + Min + " max value = " + Max + "\n Std deviation = " + StdD;       document.tournform.OutputField.value = OutText; } </script> </head> <body onload="startup()"> <form name="tournform" onSubmit="calculate();return false;">   <table width="550" height="228">     <tr>       <td colspan="3" width="500" height="24">         <b><big>Test Rubato:</big></b>       </td>     </tr>     <tr>             <td width="347"><input type=button name="Compute" value="Compute" onClick="calculate()"></td>     </tr>     <tr>     <td colspan=3 width="500" height="167">       <textarea name="OutputField" rows="21" cols="80"></textarea></td></tr>   </table> </form> </form> <p><font size="4">This script tests a random number generator 10000 times and displays the results.</font><br> </body> </html>```

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