CSCI A113
Lab Notes Seven

Fall 2001

Experiments.

What's the purpose of today's lab? To help with the homework assignment.

I think I've heard that before. Good for you.
OK, let's get started. How many coins do you need to throw?
One thousand. And how many times will you be doing that?
One thousand times. Do you really need to throw them that many times?
Yes, that gives us "smoothness on the vertical". Increasing the number of trials, that is.
With many attempts the histogram is a histogram of skyscrapers, whose heights is much bigger than the height of the bricks they're made of. With few tries it's just a histogram of a few bricks put one on top of another. The height of a brick is very important and it can influence your results.
Bicker-bicker, I don't understand any of that. Alright, it means you do need 1000 (one thousand) trials or more.
Fine, do I really need 1000 (one thousand) coins. No, not really. About 40 would be enough.
That few? How do I know that? Section 7.3 in Middleton, step 2.
What does it say? Start with mean minus four standard deviations, and use increments of about one tenth of the standard deviation.
That means 40 on each side, so 80 overall, right? Yes, sorry about that, you're right.
So we use 80 coins? Yes, 80 or even 100 would be enough.
Then what? Then you plot your distribution and look at it.
What am I looking for? You should be checking the cumulative relative frequency in the following spots:
  • mean - 3 * stdev
  • mean - 2 * stdev
  • mean - stdev
  • mean
  • mean + stdev
  • mean + 2 * stdev
  • mean + 3 * stdev
And I should be finding this values? You sure should.
Well, OK, I think I can do that. Then what? Then write a report.
And turn the report in? Yes, turn it in, today in lab or tomorrow in lecture.
What should the report contain? One page description of your conclusions.
So that's when it's due: tomorrow? Tomorrow would be fine.
Is that listed on the web site already? It now is. See you in class.

Last updated: Nov 14, 2001 by Adrian German for A113