Calculating demand distribution of multi-step process












2












$begingroup$


It's been years since I've had to work with probabilities and I need to model a business problem, my situation is this: users are signing up for a service and I need to estimate future service requirements. I have an aggregate estimate of service signups over a period but but now I need to estimate both the likelihood of a particular prospect becoming a customer, as well as their future service needs.



Example

Step 1: 100 Prospects

Step 2: 30% will sign up over a 30 day period (a distribution)

Step 3: Survey Customer location and develop proposal (capacity: 2/day starting from sign-up)

Step 4: Customer signs off on proposal (a distribution, assume 1-10 days)

Step 5: Construction (capacity: 2/day, starting from sign-off)

Step 6: Set up service (capacity: 3/day, starting from construction completion)



The goal is to generate a demand-distribution for each step of the process.



In this example, a lot of this is driven by Step 2 and 4. Given the probability distribution of these steps, it drives demand for steps 3, 5 and 6, though daily capacity also figures. Also worth noting, I need to project demand by zipcode so (I think) I need to figure demand for each prospect, not just aggregate.



Finally, we'll start with an estimate but it needs to adjust for reality, So for example, on day 0 all 100 might have 1% chance of signing up, however on day 1, 10 sign up (say we get lucky), on day 2, those 10 now have 0% (because they've signed). While the remaining 90 still have 1%. Given this scenario, we might expect that greater than 30% will sign up in the 30-day period and adjust our probabilities upward.












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$endgroup$

















    2












    $begingroup$


    It's been years since I've had to work with probabilities and I need to model a business problem, my situation is this: users are signing up for a service and I need to estimate future service requirements. I have an aggregate estimate of service signups over a period but but now I need to estimate both the likelihood of a particular prospect becoming a customer, as well as their future service needs.



    Example

    Step 1: 100 Prospects

    Step 2: 30% will sign up over a 30 day period (a distribution)

    Step 3: Survey Customer location and develop proposal (capacity: 2/day starting from sign-up)

    Step 4: Customer signs off on proposal (a distribution, assume 1-10 days)

    Step 5: Construction (capacity: 2/day, starting from sign-off)

    Step 6: Set up service (capacity: 3/day, starting from construction completion)



    The goal is to generate a demand-distribution for each step of the process.



    In this example, a lot of this is driven by Step 2 and 4. Given the probability distribution of these steps, it drives demand for steps 3, 5 and 6, though daily capacity also figures. Also worth noting, I need to project demand by zipcode so (I think) I need to figure demand for each prospect, not just aggregate.



    Finally, we'll start with an estimate but it needs to adjust for reality, So for example, on day 0 all 100 might have 1% chance of signing up, however on day 1, 10 sign up (say we get lucky), on day 2, those 10 now have 0% (because they've signed). While the remaining 90 still have 1%. Given this scenario, we might expect that greater than 30% will sign up in the 30-day period and adjust our probabilities upward.












    share|cite|improve this question











    $endgroup$















      2












      2








      2





      $begingroup$


      It's been years since I've had to work with probabilities and I need to model a business problem, my situation is this: users are signing up for a service and I need to estimate future service requirements. I have an aggregate estimate of service signups over a period but but now I need to estimate both the likelihood of a particular prospect becoming a customer, as well as their future service needs.



      Example

      Step 1: 100 Prospects

      Step 2: 30% will sign up over a 30 day period (a distribution)

      Step 3: Survey Customer location and develop proposal (capacity: 2/day starting from sign-up)

      Step 4: Customer signs off on proposal (a distribution, assume 1-10 days)

      Step 5: Construction (capacity: 2/day, starting from sign-off)

      Step 6: Set up service (capacity: 3/day, starting from construction completion)



      The goal is to generate a demand-distribution for each step of the process.



      In this example, a lot of this is driven by Step 2 and 4. Given the probability distribution of these steps, it drives demand for steps 3, 5 and 6, though daily capacity also figures. Also worth noting, I need to project demand by zipcode so (I think) I need to figure demand for each prospect, not just aggregate.



      Finally, we'll start with an estimate but it needs to adjust for reality, So for example, on day 0 all 100 might have 1% chance of signing up, however on day 1, 10 sign up (say we get lucky), on day 2, those 10 now have 0% (because they've signed). While the remaining 90 still have 1%. Given this scenario, we might expect that greater than 30% will sign up in the 30-day period and adjust our probabilities upward.












      share|cite|improve this question











      $endgroup$




      It's been years since I've had to work with probabilities and I need to model a business problem, my situation is this: users are signing up for a service and I need to estimate future service requirements. I have an aggregate estimate of service signups over a period but but now I need to estimate both the likelihood of a particular prospect becoming a customer, as well as their future service needs.



      Example

      Step 1: 100 Prospects

      Step 2: 30% will sign up over a 30 day period (a distribution)

      Step 3: Survey Customer location and develop proposal (capacity: 2/day starting from sign-up)

      Step 4: Customer signs off on proposal (a distribution, assume 1-10 days)

      Step 5: Construction (capacity: 2/day, starting from sign-off)

      Step 6: Set up service (capacity: 3/day, starting from construction completion)



      The goal is to generate a demand-distribution for each step of the process.



      In this example, a lot of this is driven by Step 2 and 4. Given the probability distribution of these steps, it drives demand for steps 3, 5 and 6, though daily capacity also figures. Also worth noting, I need to project demand by zipcode so (I think) I need to figure demand for each prospect, not just aggregate.



      Finally, we'll start with an estimate but it needs to adjust for reality, So for example, on day 0 all 100 might have 1% chance of signing up, however on day 1, 10 sign up (say we get lucky), on day 2, those 10 now have 0% (because they've signed). While the remaining 90 still have 1%. Given this scenario, we might expect that greater than 30% will sign up in the 30-day period and adjust our probabilities upward.









      probability probability-distributions






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      edited Jul 29 '13 at 1:32







      stephano

















      asked Jul 28 '13 at 22:53









      stephanostephano

      112




      112






















          1 Answer
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          0












          $begingroup$

          There are two interpretations of this. The first is if you just care about the number of users signed up on given days. This is essentially a multinomial distribution. We have $d=30$ days. Each user goes into a particular day and we have something like $n=30$ users. The chance that a user goes into a day is independent of anyone else and is equal throughout all days, and is equal to $p=1/d$. Let $N=(n_1,n_2,ldots,n_d)$ be the vector of users where $n_i$ is the number of users signed up on day $i$. Clearly $sum_{i=1}^dn_i=n$. Then



          $$P(N=(n_1,ldots,n_d))=frac{n!}{n_1!cdots n_d!}p^n$$



          Otherwise, if you label the users $1,2,..,n$, the chance of the users signing up on individually prescribed dates (say user 1 on day 4, user 2 on day 20, etc), is always $p^n$.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Thank you! <br/><br/>I need to develop probabilities for each customer (each customer has a zipcode and we need to project demand by zipcode). We start with a projection but then the model needs to account for actual signups. For example, on day 0 all 100 might 1% chance of signing up, however on day 1, 10 sign up (we get lucky), now on day 2 those 10 have 0% (they've signed). The remaining 90still have 1%, etc.<br/><br/> This process has about 10 steps with variable amounts of lag for each step, so the eventual goal is to generate a demand-distribution for each step of the process.
            $endgroup$
            – stephano
            Jul 29 '13 at 0:05












          • $begingroup$
            Note: I substantially updated the problem description to clarify problem after this answer was submitted (many thanks!)
            $endgroup$
            – stephano
            Jul 29 '13 at 1:35











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          1 Answer
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          1 Answer
          1






          active

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          active

          oldest

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          active

          oldest

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          0












          $begingroup$

          There are two interpretations of this. The first is if you just care about the number of users signed up on given days. This is essentially a multinomial distribution. We have $d=30$ days. Each user goes into a particular day and we have something like $n=30$ users. The chance that a user goes into a day is independent of anyone else and is equal throughout all days, and is equal to $p=1/d$. Let $N=(n_1,n_2,ldots,n_d)$ be the vector of users where $n_i$ is the number of users signed up on day $i$. Clearly $sum_{i=1}^dn_i=n$. Then



          $$P(N=(n_1,ldots,n_d))=frac{n!}{n_1!cdots n_d!}p^n$$



          Otherwise, if you label the users $1,2,..,n$, the chance of the users signing up on individually prescribed dates (say user 1 on day 4, user 2 on day 20, etc), is always $p^n$.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Thank you! <br/><br/>I need to develop probabilities for each customer (each customer has a zipcode and we need to project demand by zipcode). We start with a projection but then the model needs to account for actual signups. For example, on day 0 all 100 might 1% chance of signing up, however on day 1, 10 sign up (we get lucky), now on day 2 those 10 have 0% (they've signed). The remaining 90still have 1%, etc.<br/><br/> This process has about 10 steps with variable amounts of lag for each step, so the eventual goal is to generate a demand-distribution for each step of the process.
            $endgroup$
            – stephano
            Jul 29 '13 at 0:05












          • $begingroup$
            Note: I substantially updated the problem description to clarify problem after this answer was submitted (many thanks!)
            $endgroup$
            – stephano
            Jul 29 '13 at 1:35
















          0












          $begingroup$

          There are two interpretations of this. The first is if you just care about the number of users signed up on given days. This is essentially a multinomial distribution. We have $d=30$ days. Each user goes into a particular day and we have something like $n=30$ users. The chance that a user goes into a day is independent of anyone else and is equal throughout all days, and is equal to $p=1/d$. Let $N=(n_1,n_2,ldots,n_d)$ be the vector of users where $n_i$ is the number of users signed up on day $i$. Clearly $sum_{i=1}^dn_i=n$. Then



          $$P(N=(n_1,ldots,n_d))=frac{n!}{n_1!cdots n_d!}p^n$$



          Otherwise, if you label the users $1,2,..,n$, the chance of the users signing up on individually prescribed dates (say user 1 on day 4, user 2 on day 20, etc), is always $p^n$.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Thank you! <br/><br/>I need to develop probabilities for each customer (each customer has a zipcode and we need to project demand by zipcode). We start with a projection but then the model needs to account for actual signups. For example, on day 0 all 100 might 1% chance of signing up, however on day 1, 10 sign up (we get lucky), now on day 2 those 10 have 0% (they've signed). The remaining 90still have 1%, etc.<br/><br/> This process has about 10 steps with variable amounts of lag for each step, so the eventual goal is to generate a demand-distribution for each step of the process.
            $endgroup$
            – stephano
            Jul 29 '13 at 0:05












          • $begingroup$
            Note: I substantially updated the problem description to clarify problem after this answer was submitted (many thanks!)
            $endgroup$
            – stephano
            Jul 29 '13 at 1:35














          0












          0








          0





          $begingroup$

          There are two interpretations of this. The first is if you just care about the number of users signed up on given days. This is essentially a multinomial distribution. We have $d=30$ days. Each user goes into a particular day and we have something like $n=30$ users. The chance that a user goes into a day is independent of anyone else and is equal throughout all days, and is equal to $p=1/d$. Let $N=(n_1,n_2,ldots,n_d)$ be the vector of users where $n_i$ is the number of users signed up on day $i$. Clearly $sum_{i=1}^dn_i=n$. Then



          $$P(N=(n_1,ldots,n_d))=frac{n!}{n_1!cdots n_d!}p^n$$



          Otherwise, if you label the users $1,2,..,n$, the chance of the users signing up on individually prescribed dates (say user 1 on day 4, user 2 on day 20, etc), is always $p^n$.






          share|cite|improve this answer











          $endgroup$



          There are two interpretations of this. The first is if you just care about the number of users signed up on given days. This is essentially a multinomial distribution. We have $d=30$ days. Each user goes into a particular day and we have something like $n=30$ users. The chance that a user goes into a day is independent of anyone else and is equal throughout all days, and is equal to $p=1/d$. Let $N=(n_1,n_2,ldots,n_d)$ be the vector of users where $n_i$ is the number of users signed up on day $i$. Clearly $sum_{i=1}^dn_i=n$. Then



          $$P(N=(n_1,ldots,n_d))=frac{n!}{n_1!cdots n_d!}p^n$$



          Otherwise, if you label the users $1,2,..,n$, the chance of the users signing up on individually prescribed dates (say user 1 on day 4, user 2 on day 20, etc), is always $p^n$.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Jul 28 '13 at 23:54

























          answered Jul 28 '13 at 23:41









          Alex R.Alex R.

          25k12452




          25k12452












          • $begingroup$
            Thank you! <br/><br/>I need to develop probabilities for each customer (each customer has a zipcode and we need to project demand by zipcode). We start with a projection but then the model needs to account for actual signups. For example, on day 0 all 100 might 1% chance of signing up, however on day 1, 10 sign up (we get lucky), now on day 2 those 10 have 0% (they've signed). The remaining 90still have 1%, etc.<br/><br/> This process has about 10 steps with variable amounts of lag for each step, so the eventual goal is to generate a demand-distribution for each step of the process.
            $endgroup$
            – stephano
            Jul 29 '13 at 0:05












          • $begingroup$
            Note: I substantially updated the problem description to clarify problem after this answer was submitted (many thanks!)
            $endgroup$
            – stephano
            Jul 29 '13 at 1:35


















          • $begingroup$
            Thank you! <br/><br/>I need to develop probabilities for each customer (each customer has a zipcode and we need to project demand by zipcode). We start with a projection but then the model needs to account for actual signups. For example, on day 0 all 100 might 1% chance of signing up, however on day 1, 10 sign up (we get lucky), now on day 2 those 10 have 0% (they've signed). The remaining 90still have 1%, etc.<br/><br/> This process has about 10 steps with variable amounts of lag for each step, so the eventual goal is to generate a demand-distribution for each step of the process.
            $endgroup$
            – stephano
            Jul 29 '13 at 0:05












          • $begingroup$
            Note: I substantially updated the problem description to clarify problem after this answer was submitted (many thanks!)
            $endgroup$
            – stephano
            Jul 29 '13 at 1:35
















          $begingroup$
          Thank you! <br/><br/>I need to develop probabilities for each customer (each customer has a zipcode and we need to project demand by zipcode). We start with a projection but then the model needs to account for actual signups. For example, on day 0 all 100 might 1% chance of signing up, however on day 1, 10 sign up (we get lucky), now on day 2 those 10 have 0% (they've signed). The remaining 90still have 1%, etc.<br/><br/> This process has about 10 steps with variable amounts of lag for each step, so the eventual goal is to generate a demand-distribution for each step of the process.
          $endgroup$
          – stephano
          Jul 29 '13 at 0:05






          $begingroup$
          Thank you! <br/><br/>I need to develop probabilities for each customer (each customer has a zipcode and we need to project demand by zipcode). We start with a projection but then the model needs to account for actual signups. For example, on day 0 all 100 might 1% chance of signing up, however on day 1, 10 sign up (we get lucky), now on day 2 those 10 have 0% (they've signed). The remaining 90still have 1%, etc.<br/><br/> This process has about 10 steps with variable amounts of lag for each step, so the eventual goal is to generate a demand-distribution for each step of the process.
          $endgroup$
          – stephano
          Jul 29 '13 at 0:05














          $begingroup$
          Note: I substantially updated the problem description to clarify problem after this answer was submitted (many thanks!)
          $endgroup$
          – stephano
          Jul 29 '13 at 1:35




          $begingroup$
          Note: I substantially updated the problem description to clarify problem after this answer was submitted (many thanks!)
          $endgroup$
          – stephano
          Jul 29 '13 at 1:35


















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