Poisson Cookes

Get Data

The data are available on line. We download the CSV file.

  cookies <- read.csv("http://facweb1.redlands.edu/fac/jim_bentley/data/math311/poissoncookies/keebler2017.csv", header=TRUE)
cookies$Student <- as.factor(cookies$Student)
  head(cookies)

##   Chips  Bag Student
## 1     8 Bugs       1
## 2     8 Bugs       1
## 3     7 Bugs       1
## 4    10 Bugs       1
## 5     9 Bugs       1
## 6    13 Bugs       1

Compute Descriptive Statistics

We compute descriptive statistics. The use of “by” makes computing stats for subsets of the data easy.

  sum(cookies$Chips)

## [1] 490

  length(cookies$Chips)

## [1] 53

  mean(cookies$Chips)

## [1] 9.245283

  var(cookies$Chips)

## [1] 6.534833

  ### Now subset by bag
  by(cookies$Chips, cookies$Bag, sum)

## cookies$Bag: Bugs
## [1] 223
## -------------------------------------------------------- 
## cookies$Bag: Mixed
## [1] 36
## -------------------------------------------------------- 
## cookies$Bag: NoBugs
## [1] 231

  by(cookies$Chips, cookies$Bag, mean)

## cookies$Bag: Bugs
## [1] 9.291667
## -------------------------------------------------------- 
## cookies$Bag: Mixed
## [1] 9
## -------------------------------------------------------- 
## cookies$Bag: NoBugs
## [1] 9.24

  by(cookies$Chips, cookies$Bag, var)

## cookies$Bag: Bugs
## [1] 7.780797
## -------------------------------------------------------- 
## cookies$Bag: Mixed
## [1] 0.6666667
## -------------------------------------------------------- 
## cookies$Bag: NoBugs
## [1] 6.606667

  table(cookies$Chips)

## 
##  5  6  7  8  9 10 11 12 13 14 16 
##  5  2  6  8  9  9  3  5  3  2  1

  table(cookies$Chips, cookies$Bag) ### Compute counts

##     
##      Bugs Mixed NoBugs
##   5     3     0      2
##   6     1     0      1
##   7     3     0      3
##   8     4     1      3
##   9     1     2      6
##   10    4     1      4
##   11    1     0      2
##   12    3     0      2
##   13    3     0      0
##   14    1     0      1
##   16    0     0      1

  ### Plots
  p_load(lattice)
  histogram(~Chips|Bag, data=cookies, layout=c(1,3), type="count")