Probability Question (Not About Sports)

NYSportsGuy210 · 02-19-12, 10:41 PM

With or without replacement? Also depends if they are selected first and third or first and second.

NYSportsGuy210 · 02-19-12, 10:44 PM

6/15*5/14*8/13 if it's two light bulbs exactly first and second.

6/15*9/14*5/13 if the two light bulbs selected are first and third.

daneault23 · 02-19-12, 10:48 PM

NYer, the question says you pick 3 light bulbs and 2 of them are 75 watters. I doesn't mention anything about what order u pick them.

This is directly from my stats book as this is my 1st hw question and I think I am overthinking things here.

NYSportsGuy210 · 02-19-12, 10:51 PM

Dude use your head to do the math. It's not that difficult....just break it down one at a time.

Odd of picking a 75 watter the first time are 6/15. Now with out replacement odds of picking it a second time are 5/14. On the third time you don't wanna pick it so it's 9/13. Multiply all three together.

Don't be a lil b*tch.

daneault23 · 02-19-12, 10:59 PM

Haha NYer you fukk, you're right man. I was totally overthinking this shit. Here's a few points to go blow in the casino

hokim · 02-19-12, 11:07 PM

Without replacement, the number of all possible cases is 15C3 (15 combination 3). The number of cases that you pick 2 75Ws and any one else is 6C2*9C1.

The answer is 6C2*9C1/15C3 = 27/91

daneault23 · 02-19-12, 11:19 PM

hokim, I believe ur actually right. NYer, while your explanation makes sense somewhat, hokim's response is similar to what is shown in the book and so I'm goin with his answer.

NYSportsGuy210 · 02-19-12, 11:27 PM

If you learned the formula for Combination and Permutation that can also be applied in this case. I just forgot them exactly off hand plus I am too tired to think right now. Been reading books on fundamental analysis all day and browsing the internet like a lazy bum.

NYSportsGuy210 · 02-19-12, 11:30 PM

27/91 is almost one-third. I think the chances of picking this at one third seems a little too high to me.

daneault23 · 02-20-12, 12:04 AM

NYer the formulas for permutations and combinations are what Im supposed to use to answer these questions, I just wasn't sure what the numbers would be for the first case. Imma go to that bitches office tomorrow anyways and ask her a few questions, so it's all good.

TheCentaur · 02-20-12, 12:19 AM

It's not necessary to know how to do this to win at gambling.
Are the 75 watt bulb boxes bigger than the others?

hokim · 02-20-12, 02:30 AM

NYSportsGuy's approach is also correct and you will get the same answer.

6/15*5/14*9/13 + 6/15*9/14*5/13 + 9/15*6/14*5/13 = 3*(6*5*9)/(15*14*13) = 27/91