New Posts For Thread: Question from a Maths Forum, what do you think is the answer?https://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answerI came across this question by chance on a maths forum. I would be interested to see what the answer is generally thought to be. I have my view which doesn't match that given. The journey to or from work has a mean of 67 minutes and a standard deviatContrarian & Bayes,Thanks for that, I know the basic Bayes but wasn't aware of the point about the SD for multiple events.As I said I don't think they independent events, but pleased to learn something new anyway.Have a good Xmas.https://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479123157#479123157Contrarian & Bayes,Thanks for that, I know the basic Bayes but wasn't aware of the point about the SD for multiple events.As I said I don't think they independent events, but pleased to learn something new anyway.Have a good Xmas.Thu, 23 Dec 2010 10:05:43 -0600Equimine,Your experts answer is wrong. What Bayes is saying is basically that if you double the number of samples (in your example, 'samples' are time periods), then the SD increases by a factor of the square root of 2 (because SD is the root of varihttps://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479116797#479116797Equimine,Your experts answer is wrong. What Bayes is saying is basically that if you double the number of samples (in your example, 'samples' are time periods), then the SD increases by a factor of the square root of 2 (because SD is the root of variThu, 23 Dec 2010 08:41:53 -0600Thanks for your comments. The experts answer is double the mean time and the SD to get the z score. So z=(151-134)/30 = 0.57, which gives .2843.I do not think you can answer the question as worded, the journey times are not in, my view, independent.Bhttps://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479115825#479115825Thanks for your comments. The experts answer is double the mean time and the SD to get the z score. So z=(151-134)/30 = 0.57, which gives .2843.I do not think you can answer the question as worded, the journey times are not in, my view, independent.BThu, 23 Dec 2010 08:28:21 -0600The standard deviation comes from:SD(X + X) = sqrt( Var(X) + Var(X))The above only applies if the covariance of the two events (the trip to work and the trip home) is zero. If the times are independent then this is the case. Are the journey times ofhttps://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479106089#479106089The standard deviation comes from:SD(X + X) = sqrt( Var(X) + Var(X))The above only applies if the covariance of the two events (the trip to work and the trip home) is zero. If the times are independent then this is the case. Are the journey times ofThu, 23 Dec 2010 05:49:28 -0600Bayes is right. Mean for total journey is 134 mins, sd is 21.21. So prob = (in Excel) (1 - NORMDIST(151, 134, 21.21, TRUE))https://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479103149#479103149Bayes is right. Mean for total journey is 134 mins, sd is 21.21. So prob = (in Excel) (1 - NORMDIST(151, 134, 21.21, TRUE))Thu, 23 Dec 2010 04:55:21 -06000.211 assuming that the journey times are independent, which in a case like this is unlikely to be true.https://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479101617#4791016170.211 assuming that the journey times are independent, which in a case like this is unlikely to be true.Thu, 23 Dec 2010 04:14:47 -06000.00https://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479100993#4791009930.00Thu, 23 Dec 2010 03:54:54 -0600I came across this question by chance on a maths forum. I would be interested to see what the answer is generally thought to be. I have my view which doesn't match that given. The journey to or from work has a mean of 67 minutes and a standard deviathttps://community.betfair.com/general_betting/go/thread/view/94082/26505701/question-from-a-maths-forum-what-do-you-think-is-the-answer?post_id=479100729#479100729I came across this question by chance on a maths forum. I would be interested to see what the answer is generally thought to be. I have my view which doesn't match that given. The journey to or from work has a mean of 67 minutes and a standard deviatThu, 23 Dec 2010 03:46:04 -0600