# Thread: mind exercise

1. ## mind exercise

This exercise is sort of related to testing. If you can solve this problem, you are an obvious master of boundary analysis and minimizing the number of test cases to be run.

You have 3 boxes. Each has 2 marbles. One box has two black marbles, one has 2 white marbles and one has a black and a white marble.

Each box is labeled as to it's contents - BB, BW, WW. However each label is on the wrong box.

Reaching into a box and drawing out a single marble to determine it's colors, specify the minimum number of draws and the sequence of the draws in order to correctly label each box as to it's contents.

2. ## Re: mind exercise

When you draw a marble from a box, do you keep the marble outside or do you return it?
If you have to return the marble each time, you will never KNOW correctly the contents of all boxes, just have a probability figure.

3. ## Re: mind exercise

I think that it is a given that the marble stays out of the box, don't you?

Sounds like a diversionery tactic to me.

4. ## Re: mind exercise

Ahem. A good tester (or designer/developer) never makes assumptions if a simple question/answer session will clarify the issue! [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img]

Plus, you are assuming that I didn't have an answer for both interpretations.
When keeping each marble when picked, 3-best case, 4-worst case. I won't give my reasoning or method yet, in case others are still working on it.
If the marble goes back each time, 30 (10 per box) would give you a high probability of being correct (a good round figure for using Chi Squared).

[ 06-14-2004, 08:44 PM: Message edited by: KBEE01 ]

5. ## Re: mind exercise

I want to claim the first answer, but don't want to post it for fear of ruining the question.

Thanks for waking me up on a dark Monday.

6. ## Re: mind exercise

Anyone can email me the answer, if they like. Go to my profile and there is a mail link on my home page.

7. ## Re: mind exercise

Does the marble stay out or not? Well.....

If I tell you, it will give away the answer. But, I will take the chance. The answer is....
it doesn't matter.

2 draws....

- Linda

1 draw

10. ## Re: mind exercise

qasleuth is correct. Now, what is the draw?

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