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A local store opens at 6:00am every day. Suppose that there is one customer comi

ID: 3220577 • Letter: A

Question

A local store opens at 6:00am every day. Suppose that there is one customer coming to the store at each minute with probability 0.02 Let X be the time until the first customer comes to the store once it is opened. Find the PMF of X and E[X]? Given that there is not any customer for the first 1 hour since it is opened and let Y be the time until the first customer comes after the first 1 hour since it is opened. Find E[Y]? Suppose that there is one customer coming to the store every 10 minutes on the average. 1. Find the probability that there are no customer coming to the store between 6:00am and 7:00am? 2. Find the probability that there are at least 2 customers coming to the store between 6:00am and 7:00am?

Explanation / Answer

a)

            1)Given probability P=0.02

            Let X be time in minutes and X= 1,2,3....... min (until customer come to the store)

            Probability of mass function P(X) =e-m.mx /X!

                                                            = e-1.1x /X!   (since m=1, mean number of customer )

                                                            = e-1/X!  

                                                E(X)    = e-1/1!   + e-1/2!   + e-1/3!   + e-1/4!   ...............

            2) given that no customer for 1 hour(60 minuts)

                                                            n=60 min

                                                            m=n.P =60*0.02

                                                            =1.2

                                                P(Y) = e-m.my /Y!

                                                P(0)= e-1.2(1.2)0 /0!

                                                        = e-1.2      

                                                        =0.3012

                                                E(Y)=0.3012

b. given that there are 1 customer for every 10 minutes, so 6customers for 1 hour (time taken hours here)                         m=6

            1.Probability of no customer coming between 6:00 to 7:00

                                    X=0, m=6,

                                                P(X=0)= e-m.mx /X!

                                                        = e-660 /0! =e-6

                                                        =0.00247

                                    P(X=0) =0.00247

            2)Probability of at least 2 customer between 6:00 to 7:00

                                    P(X2) = 1-P(X<2)

= 1- [ P(X=0)+ P(X=1)]

                                                =1-[ e-660 /0! + e-661 /1! ]

                                                            = 1-[0.00247+0.01487]

                                                            =0.9827

                                                            =98.27%

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