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Re: probability problems

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Mon, 7 Feb 2011 23:04:22 +0000

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 ```i would say 1b is 5/6 and 1c is 0!? On 7 February 2011 22:06, Andre Francis <[log in to unmask]> wrote: > Q1. If 1 = defective. > > 1a p(11) = 2/4x1/3 = 1/6 > > 1b p(101 or 011) = 2/4x2/3x1/2x2 = 1/3 > > 1c 1- (1a + 1b) = 1 - (1/6 + 1/3) = 1/2 > > > > Q2 The information given yields (for a population of 400): n(U and T)=57; > n(NotU and T)=120; n(U and NotT)=3 where U = 'upper class' and T = > TV-owning. The above can be seen to give: a 6/17 b 177/400 c 19/59 > > > > Q3 The problem is essentially p(> 25 connections / minute). If we consider > a > connection as the start of a call and a 'rush hour' as precisely 1 hour, > then the probability can be calculated using a Poisson distribution, mean > 500/60 = 8.33 ..... which yields probability zero (Am I missing something?) > What if there were 26 calls at 1-second intervals, each lasting for less > than 1 second? Would this overtax the board? ... and so on! > > > I hope this is of some use > > > Andre Francis > > > > On 7 February 2011 15:36, marina garcia <[log in to unmask]> > wrote: > > > hi allstat, > > > > pls kindly help me with these probability problems: > > > > 1. Two defective tubes got mixed up with two good ones. The tubes > > are tested one by one until both defectives are found. > > > > a)What is the probability that both defectives have been found by > > the second test? > > b)What is the probability that three tests are required? > > c)What is the probability that four tests are required? > > > > 2. In a certain city, 15% of the households are classified as being > > of the “upper class”, according to socio-economic criteria. In > > addition, it is known that 95% of upper-class households own > > colored television sets. It is known that 30% of households that > > are not of upper-class status own a TV set. If a sample household > > is to be selected for interview such that all the households of > > the city are equally likely to be selected, find the probability > > that > > a) it does not belong to the upper class but owns a colored > > television set. > > b) it owns a colored television set. > > c) it belongs to the upper class, given that it owns a TV set. > > > > 3. A telephone switchboard handles 500 calls, on an average, during a > > rush hour. The board can make a maximum of 25 connections per > > minute. Evaluate the probability that the board will be overtaxed > > during any given minute. > > > > > > pls pm me the solutions or links to problems similar to the given > > above, if possible, with solutions... > > > > your help is highly appreciated...thanks a lot > > > > marina garcia > > uplb, philippines > > > > > > > > > > -- > > _______________________________________________ > > Surf the Web in a faster, safer and easier way: > > Download Opera 9 at http://www.opera.com > > > > You may leave the list at any time by sending the command > > > > SIGNOFF allstat > > > > to [log in to unmask], leaving the subject line blank. > > > > You may leave the list at any time by sending the command > > SIGNOFF allstat > > to [log in to unmask], leaving the subject line blank. > You may leave the list at any time by sending the command SIGNOFF allstat to [log in to unmask], leaving the subject line blank. ```