Compute the probability of waiting more than $30$ seconds for the next call.

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Question: At ABC insurance company, suppose the patient insurance inquiries arrive at mean rate of $2.2$ calls per minute. Compute the probability of waiting more than $30$ seconds for the next call.




I am confused here.
When I first read the question, I thought of modelling the situation using Poisson distribution because of $2.2$ calls per minute.
However, the question is asking for time between two calls, which is not discrete.



If I follow my initial thought to solve the question, then define $X$ to be the number of calls per $30$ seconds, then from the question, $lambda = 2.2 /2 = 1.1.$
Then I think we need to calculate $mathbbP(X = 1).$










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  • The Poisson model is appropriate. Under this model, the time until the next call follows an exponential distribution with mean $frac12.2$.
    – Yuta
    Sep 6 at 5:11







  • 1




    Waiting more than $30$ seconds for the next call means there is no calls in the first $30$-second interval. So the required probability should be $mathbbP(X=0)$.
    – Yuta
    Sep 6 at 5:17















up vote
0
down vote

favorite













Question: At ABC insurance company, suppose the patient insurance inquiries arrive at mean rate of $2.2$ calls per minute. Compute the probability of waiting more than $30$ seconds for the next call.




I am confused here.
When I first read the question, I thought of modelling the situation using Poisson distribution because of $2.2$ calls per minute.
However, the question is asking for time between two calls, which is not discrete.



If I follow my initial thought to solve the question, then define $X$ to be the number of calls per $30$ seconds, then from the question, $lambda = 2.2 /2 = 1.1.$
Then I think we need to calculate $mathbbP(X = 1).$










share|cite|improve this question























  • The Poisson model is appropriate. Under this model, the time until the next call follows an exponential distribution with mean $frac12.2$.
    – Yuta
    Sep 6 at 5:11







  • 1




    Waiting more than $30$ seconds for the next call means there is no calls in the first $30$-second interval. So the required probability should be $mathbbP(X=0)$.
    – Yuta
    Sep 6 at 5:17













up vote
0
down vote

favorite









up vote
0
down vote

favorite












Question: At ABC insurance company, suppose the patient insurance inquiries arrive at mean rate of $2.2$ calls per minute. Compute the probability of waiting more than $30$ seconds for the next call.




I am confused here.
When I first read the question, I thought of modelling the situation using Poisson distribution because of $2.2$ calls per minute.
However, the question is asking for time between two calls, which is not discrete.



If I follow my initial thought to solve the question, then define $X$ to be the number of calls per $30$ seconds, then from the question, $lambda = 2.2 /2 = 1.1.$
Then I think we need to calculate $mathbbP(X = 1).$










share|cite|improve this question
















Question: At ABC insurance company, suppose the patient insurance inquiries arrive at mean rate of $2.2$ calls per minute. Compute the probability of waiting more than $30$ seconds for the next call.




I am confused here.
When I first read the question, I thought of modelling the situation using Poisson distribution because of $2.2$ calls per minute.
However, the question is asking for time between two calls, which is not discrete.



If I follow my initial thought to solve the question, then define $X$ to be the number of calls per $30$ seconds, then from the question, $lambda = 2.2 /2 = 1.1.$
Then I think we need to calculate $mathbbP(X = 1).$







probability poisson-distribution






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edited Sep 6 at 5:11

























asked Sep 6 at 5:08









Idonknow

3,115644109




3,115644109











  • The Poisson model is appropriate. Under this model, the time until the next call follows an exponential distribution with mean $frac12.2$.
    – Yuta
    Sep 6 at 5:11







  • 1




    Waiting more than $30$ seconds for the next call means there is no calls in the first $30$-second interval. So the required probability should be $mathbbP(X=0)$.
    – Yuta
    Sep 6 at 5:17

















  • The Poisson model is appropriate. Under this model, the time until the next call follows an exponential distribution with mean $frac12.2$.
    – Yuta
    Sep 6 at 5:11







  • 1




    Waiting more than $30$ seconds for the next call means there is no calls in the first $30$-second interval. So the required probability should be $mathbbP(X=0)$.
    – Yuta
    Sep 6 at 5:17
















The Poisson model is appropriate. Under this model, the time until the next call follows an exponential distribution with mean $frac12.2$.
– Yuta
Sep 6 at 5:11





The Poisson model is appropriate. Under this model, the time until the next call follows an exponential distribution with mean $frac12.2$.
– Yuta
Sep 6 at 5:11





1




1




Waiting more than $30$ seconds for the next call means there is no calls in the first $30$-second interval. So the required probability should be $mathbbP(X=0)$.
– Yuta
Sep 6 at 5:17





Waiting more than $30$ seconds for the next call means there is no calls in the first $30$-second interval. So the required probability should be $mathbbP(X=0)$.
– Yuta
Sep 6 at 5:17











1 Answer
1






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I believe you can solve using either.



Using Poisson



Let $X$ be the number of calls in $30$ seconds. Then $X sim Poisson(lambda = 1.1)$ and $P(X=0) = e^-1.1$



Using Exponential



Let $Y$ be the time until the first call. The average time to the first call is $60/2.2 = 27.27$ seconds.



That means $E[Y] = 27.27$ which means $frac1lambda = 27.27$ so $lambda = .0366$ and then $P(Y > 30) = 1-P(Y le 30) = 1-(1-e^-30 *.0366) = e^-1.1$




I think the key thing is that $lambda$ is a rate parameter so if someone says $2.2$ every minute you can chop it up to suit your needs... I am learning this stuff as well so let me know if you have any doubts.






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    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    1
    down vote



    accepted










    I believe you can solve using either.



    Using Poisson



    Let $X$ be the number of calls in $30$ seconds. Then $X sim Poisson(lambda = 1.1)$ and $P(X=0) = e^-1.1$



    Using Exponential



    Let $Y$ be the time until the first call. The average time to the first call is $60/2.2 = 27.27$ seconds.



    That means $E[Y] = 27.27$ which means $frac1lambda = 27.27$ so $lambda = .0366$ and then $P(Y > 30) = 1-P(Y le 30) = 1-(1-e^-30 *.0366) = e^-1.1$




    I think the key thing is that $lambda$ is a rate parameter so if someone says $2.2$ every minute you can chop it up to suit your needs... I am learning this stuff as well so let me know if you have any doubts.






    share|cite|improve this answer


























      up vote
      1
      down vote



      accepted










      I believe you can solve using either.



      Using Poisson



      Let $X$ be the number of calls in $30$ seconds. Then $X sim Poisson(lambda = 1.1)$ and $P(X=0) = e^-1.1$



      Using Exponential



      Let $Y$ be the time until the first call. The average time to the first call is $60/2.2 = 27.27$ seconds.



      That means $E[Y] = 27.27$ which means $frac1lambda = 27.27$ so $lambda = .0366$ and then $P(Y > 30) = 1-P(Y le 30) = 1-(1-e^-30 *.0366) = e^-1.1$




      I think the key thing is that $lambda$ is a rate parameter so if someone says $2.2$ every minute you can chop it up to suit your needs... I am learning this stuff as well so let me know if you have any doubts.






      share|cite|improve this answer
























        up vote
        1
        down vote



        accepted







        up vote
        1
        down vote



        accepted






        I believe you can solve using either.



        Using Poisson



        Let $X$ be the number of calls in $30$ seconds. Then $X sim Poisson(lambda = 1.1)$ and $P(X=0) = e^-1.1$



        Using Exponential



        Let $Y$ be the time until the first call. The average time to the first call is $60/2.2 = 27.27$ seconds.



        That means $E[Y] = 27.27$ which means $frac1lambda = 27.27$ so $lambda = .0366$ and then $P(Y > 30) = 1-P(Y le 30) = 1-(1-e^-30 *.0366) = e^-1.1$




        I think the key thing is that $lambda$ is a rate parameter so if someone says $2.2$ every minute you can chop it up to suit your needs... I am learning this stuff as well so let me know if you have any doubts.






        share|cite|improve this answer














        I believe you can solve using either.



        Using Poisson



        Let $X$ be the number of calls in $30$ seconds. Then $X sim Poisson(lambda = 1.1)$ and $P(X=0) = e^-1.1$



        Using Exponential



        Let $Y$ be the time until the first call. The average time to the first call is $60/2.2 = 27.27$ seconds.



        That means $E[Y] = 27.27$ which means $frac1lambda = 27.27$ so $lambda = .0366$ and then $P(Y > 30) = 1-P(Y le 30) = 1-(1-e^-30 *.0366) = e^-1.1$




        I think the key thing is that $lambda$ is a rate parameter so if someone says $2.2$ every minute you can chop it up to suit your needs... I am learning this stuff as well so let me know if you have any doubts.







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Sep 6 at 6:23

























        answered Sep 6 at 5:55









        HJ_beginner

        679215




        679215



























             

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