Testing random

[Thomas 'PointedEars' Lahn]

Chris Angelico wrote:

> On Mon, Jun 8, 2015 at 1:51 AM, Thomas 'PointedEars' Lahn
> <PointedEars at web.de> wrote:
>> Chris Angelico wrote:
>>
>>> On Sun, Jun 7, 2015 at 8:40 PM, Thomas 'PointedEars' Lahn
>>> <PointedEars at web.de> wrote:
>>>> Cecil Westerhof wrote:
>>>>> I wrote a very simple function to test random:
>>>>>     def test_random(length, multiplier = 10000):
>>>>>         number_list = length * [0]
>>>>>         for i in range(length * multiplier):
>>>>>             number_list[random.randint(0, length - 1)] += 1
>>>>>         minimum = min(number_list)
>>>>>         maximum = max(number_list)
>>>>>         return (minimum, maximum, minimum / maximum)
>>>>
>>>> As there is no guarantee that every number will occur randomly, using a
>>>> dictionary at first should be more efficient than a list:
>>>
>>> Hmm, I'm not sure that's actually so. His code is aiming to get
>>> 'multiplier' values in each box; for any serious multiplier (he starts
>>> with 10 in the main code), you can be fairly confident that every
>>> number will come up at least once.
>>
>> The wording shows a common misconception: that random distribution would
>> mean that it is guaranteed or more probable that every element of the set
>> will occur at least once.  It is another common misconception that
>> increasing the number of trials would increase the probability of that
>> happening.  But that is not so.
> 
> The greater the multiplier, the lower the chance that any element will
> have no hits.

Wrong.

> [ex falso quodlibet]

-- 
PointedEars

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