R version 3.5.1 (2018-07-02) -- "Feather Spray"
Copyright (C) 2018 The R Foundation for Statistical Computing
Platform: x86_64-w64-mingw32/x64 (64-bit)

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[Workspace loaded from ~/.RData]

> customers<-c(9,7,9,15,10,13,11,7,2,12)
> mean(customers)
[1] 9.5
> dpois(customers,9.5)
 [1] 0.130002540 0.103713937 0.130002540 0.026518985 0.123502413 0.061706224
 [7] 0.106661175 0.103713937 0.003377689 0.084440097
> prod(dpois(customers,9.5))
[1] 1.117671e-12
> store<-rep(0,11)
> for (i in 5:15){store[i]<-prod(dpois(customers,i))}
> store
 [1] 0.000000e+00 0.000000e+00 0.000000e+00 0.000000e+00 1.288171e-19
 [6] 1.946467e-16 2.024171e-14 2.968503e-13 9.751743e-13 9.842355e-13
[11] 3.823484e-13 6.751927e-14 6.150112e-15 3.187742e-16 1.016353e-17
> cbind(seq(5,15),store[5:15])
      [,1]         [,2]
 [1,]    5 1.288171e-19
 [2,]    6 1.946467e-16
 [3,]    7 2.024171e-14
 [4,]    8 2.968503e-13
 [5,]    9 9.751743e-13
 [6,]   10 9.842355e-13
 [7,]   11 3.823484e-13
 [8,]   12 6.751927e-14
 [9,]   13 6.150112e-15
[10,]   14 3.187742e-16
[11,]   15 1.016353e-17
> theta<-seq(9,10, by=.10)
> theta
 [1]  9.0  9.1  9.2  9.3  9.4  9.5  9.6  9.7  9.8  9.9 10.0
> for (i in 1:length(theta)){store[i]<-prod(dpois(customers,theta[i]))}
> cbind(theta,store[1:length(theta)])
      theta             
 [1,]   9.0 9.751743e-13
 [2,]   9.1 1.024900e-12
 [3,]   9.2 1.064875e-12
 [4,]   9.3 1.094058e-12
 [5,]   9.4 1.111762e-12
 [6,]   9.5 1.117671e-12
 [7,]   9.6 1.111845e-12
 [8,]   9.7 1.094705e-12
 [9,]   9.8 1.067002e-12
[10,]   9.9 1.029762e-12
[11,]  10.0 9.842355e-13
>