Statistics/Math Question

[Orrex]

In my tool bag I have nine black Sharpies and one silver Sharpie.

If I need a black one and I reach into my bag blindly to grab one, what are the odds that I’ll get the silver one every single damn time?

Of course, if I want the silver one, I’ll blindly draw all nine black ones first.

[chouchou]

1. Ah Yes..I've had this action quite more than a few times.

You'll pick the black ones IF you also hit the Power-Ball jackpot twice on the same day.
You are Welcome!

[3catwoman3]

2. The only thing I remember from the one statistics course...

…I was forced to suffer thru is the bigger the N the better, and the smaller the p the better. That’s it.

If I wanted to make sure I got the silver pen, I would just cheat and open my eyes.

[The Madcap]

3. It depends.

How many times do you intend to pull?

[Orrex]

4. Good question

Generally I get the silver on the first pull, keep it in hand, and am certain to draw a black one on the second pull. But if I were to return the silver one to the bag, I’d draw it again 100% of the time.

[GopherGal]

6. Yeah, what you need to do is "sample without replacement"

If you keep returning the one you draw back to the bag, your odds remain the same for each draw. So what you need to do is set aside the one you drew until you get the one you want. In statistics this is called an "urn problem" Of course, the probability calculations by statisticians don't incorporate the Murphy's Law effect that dictates the 100% rate of getting the less desired color...

[2naSalit]

5. I would...

Grab as many as I could and see if the silver one is there in my hand. If not there, grab the rest of them so I would say the answer is 2. (As confirmed by Ray Magliottzzi, the answer is 2).