Program logic bugs vs input/environmental errors

[Nick Sabalausky via Digitalmars-d]

On 10/10/2014 05:31 AM, Joseph Rushton Wakeling wrote:
> On Friday, 10 October 2014 at 06:28:06 UTC, Iain Buclaw via
> Digitalmars-d wrote:
>> http://www.wired.com/2012/12/what-does-randomness-look-like/
>
> ... yes, allowing for the reasonable expectations one can have for
> extended runs of heads in a regular 50/50 coin-flip process.
>
> Actually, related to that article, in my very first stats lecture at
> university, the first slide the lecturer showed us (on the overhead
> projector...) was, side by side, two patterns of dots each within a
> rectangular area.
>
> He asked: "Do you think these points are distributed at random?" Well,
> they pretty much looked the same to the naked eye.
>
> Then he took another transparency, which placed grids over the two
> rectangular dot-filled areas.  In one, the dots were here, there, with
> some grid squares containing no dots at all, some containing clusters,
> whatever.
>
> In the other, every single grid square contained exactly one dot.
>
> I still think that was one of the single most important lessons in
> probability that I ever had.

I like that. I actually have a similar classroom probability story too 
(involving one of the best teachers I ever had):

As part of a probability homework assignment, we were asked to flip a 
coin 100 times and write down the results. "Uhh, yea, there's no way I'm 
doing that. I'm just gonna write down a bunch of T's and F's."

Having previously played around with PRNG's (using them, not actually 
creating them), I had noticed that you do tend to get surprisingly long 
runs of one value missing, or the occasional clustering. I carefully 
used that knowledge to help me cheat.

During the next class, the teacher pointed out that "I can tell, most of 
you didn't actually flip a coin, did you? You just wrote down T's and 
F's..." Which turned out to be the whole *point* of the assignment. 
Deliberately get students to "cheat" and fake randomness - poorly - in 
order to *really* get them to understand the nature of randomness.

Then he turned to me and said, "Uhh, Nick, you actually DID flip a coin 
didn't you?" Hehe heh heh. "Nope :)" I got a good chuckle out of that.