# Math Q **URL:** \ **Category:** NYSpeed Off Topic\ **Created:** [December 18, 2007, 10:52am UTC](https://forums.speedlife.net/t/math-q/40444 "2007-12-18T10:52:57Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![cougarspeed](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/cougarspeed/32/7468_2.png) [@cougarspeed](https://forums.speedlife.net/u/cougarspeed)\ **Post date:** [December 18, 2007, 10:52am UTC](https://forums.speedlife.net/t/math-q/40444/1 "2007-12-18T10:52:57Z")
One urn contains 3 red and 7 white marbles. A second urn contains 2 red and 8 white marbles. One urn is selected and a ball drawn. The probability of selecting the first urn is 0.4 and the probability of selecting the second is 0.6. If a white ball is drawn, find the probability it came from the second urn: I would think it is .48 but that is wrong. WTF? Someone smarter explain please.Possible answers. 0.800 0.632 0.560 0.480 For a sample of size n = 60, proportion p = 0.35, and at a 95% confidence level, the lower bound of the proportion is \_\_\_\_\_. This one i have no clue what they are even asking me. None of my ideas even come close to any of the possible answers. 0.229 0.121 0.175 0.414 ---
**Author:** ![tpgsr](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/tpgsr/32/7374_2.png) [@tpgsr](https://forums.speedlife.net/u/tpgsr)\ **Post date:** [December 18, 2007, 10:54am UTC](https://forums.speedlife.net/t/math-q/40444/2 "2007-12-18T10:54:54Z")
how are they taking two urns and saying that the probability is .4 and .6? should that be a given at .5 & .5 to begin with?? I havent had to take a math class in like 4 years so maybe i am way off / just dont care. ---
**Author:** ![cougarspeed](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/cougarspeed/32/7468_2.png) [@cougarspeed](https://forums.speedlife.net/u/cougarspeed)\ **Post date:** [December 18, 2007, 10:57am UTC](https://forums.speedlife.net/t/math-q/40444/3 "2007-12-18T10:57:04Z")
Maybe one is more appealing IDK lol. I thought it would just be .8(being white marbles in 2nd urn)x.6(the probability of picking that urn). ---
**Author:** ![sureshot](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/sureshot/32/7578_2.png) [@sureshot](https://forums.speedlife.net/u/sureshot)\ **Post date:** [December 18, 2007, 10:59am UTC](https://forums.speedlife.net/t/math-q/40444/4 "2007-12-18T10:59:52Z")
is it .6 ---
**Author:** ![cougarspeed](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/cougarspeed/32/7468_2.png) [@cougarspeed](https://forums.speedlife.net/u/cougarspeed)\ **Post date:** [December 18, 2007, 11:00am UTC](https://forums.speedlife.net/t/math-q/40444/5 "2007-12-18T11:00:54Z")
0.800 0.632 0.560 0.480 These are the options. ---
**Author:** ![tpgsr](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/tpgsr/32/7374_2.png) [@tpgsr](https://forums.speedlife.net/u/tpgsr)\ **Post date:** [December 18, 2007, 11:02am UTC](https://forums.speedlife.net/t/math-q/40444/6 "2007-12-18T11:02:59Z")
logically the probability of it coming from the second urn is \> thatn the first. the second had a higher rate of selection (.6) and it also has more white and less red than the first. .48 is a bad answer ---
**Author:** ![ILCisDEAD](https://avatars.discourse-cdn.com/v4/letter/i/a87d85/32.png) [@ILCisDEAD](https://forums.speedlife.net/u/ILCisDEAD)\ **Post date:** [December 18, 2007, 11:04am UTC](https://forums.speedlife.net/t/math-q/40444/7 "2007-12-18T11:04:48Z")
> [@Mrs Claus is gonna be pissed](https://forums.speedlife.net/t/mrs-claus-is-gonna-be-pissed/40441/7): > > howd you quote from another thread and respond in this one ? IDK its really not that hard ---
**Author:** ![cougarspeed](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/cougarspeed/32/7468_2.png) [@cougarspeed](https://forums.speedlife.net/u/cougarspeed)\ **Post date:** [December 18, 2007, 11:07am UTC](https://forums.speedlife.net/t/math-q/40444/8 "2007-12-18T11:07:49Z")
Edited with a second question. I would like a soild explination please not just an answer as i would like to know why. ---
**Author:** ![Toda\_Party](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/toda_party/32/7354_2.png) [@Toda\_Party](https://forums.speedlife.net/u/Toda_Party)\ **Post date:** [December 18, 2007, 11:29am UTC](https://forums.speedlife.net/t/math-q/40444/9 "2007-12-18T11:29:34Z")
All of the above ---
**Author:** ![cougarspeed](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/cougarspeed/32/7468_2.png) [@cougarspeed](https://forums.speedlife.net/u/cougarspeed)\ **Post date:** [December 18, 2007, 11:30am UTC](https://forums.speedlife.net/t/math-q/40444/10 "2007-12-18T11:30:36Z")
Thats not helping assface.