Random 7th
March 2013
Professor Ingrid Salvesen walked to the lectern,
straightened her notes and looked out at her audience.
‘Before
we get too deep into the discussion of randomisation, I would like to ensure
that we all agree on what we mean by random.
Let me
quote from the Oxford English Dictionary, ‘ Done or happening without any plan,
purpose or regular pattern.
Now
lets think of a random number generator, perhaps a single die. If we roll it
say, one hundred times, do you think that will give us a random distribution of
the numbers one through six? Being mathematicians you will know
that it will not. In fact it will result in a Gaussian normal distribution or
bell curve and the more times you throw the die, the more perfect the bell
curve will appear.
The
formula for this curve is, as you all know:-
Most people will assume that throwing a die is a
perfect random number generator but, as we can now see, this is not the case.
In fact it is very difficult to generate random numbers.
One way
is to roll a die. Yes, I know I have just contradicted myself but this time I
am talking about a virtual die where the number is generated by a computer
program, see:-
Those of you who have more time than I have can
use this site to generate numbers between one and six, plot them on a graph and
will find that they are indeed random and the resulting plot will have no
resemblance to a bell curve. But, I hear you cry, ‘How can a predictable
machine like a computer generate truly random numbers?’ It cannot of course,
these numbers are only pseudo random.
To get
a truly random distribution you have to use a random variable, such as
atmospheric noise as the original generator. You can see this if you unplug the
aerial of a television set as the series of white dots or ‘snow’ on the screen.
Please
excuse me a moment as I have a sore throat this evening’
‘Would
you a Rowntrees Random ® Professor?’
‘Thank
you Myra, that’s very kind of you. Now, to continue.
I don’t
have much more to say on this subject except that I hope you now understand the
nature of randomness a little better and how difficult it is to achieve true
randomisation.
I do
wonder if this is why the well known publishing group, Café Three zero had so
much trouble with their recent anthology entitled Random. If you refer back to the quote from the OED
that I started with you will see that planning a random event is, in fact, an
oxymoronic task.
I will
leave you with that thought as I go out to the car park and try and find my car
which I parked in a randomly chosen spot.’
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