Chapter 3, Displaying and Describing Catagorical Data

Homework 3.3 Problem 31 Blood Pressure

Blood <- matrix(c(27,37,31,48,91,93,23,51,73),ncol=3,byrow=TRUE)
colnames(Blood) <- c("Under 30","30-49","Over 50")

rownames(Blood) <- c("Low","Normal","High")
Blood <- as.table(Blood)
Blood
##        Under 30 30-49 Over 50
## Low          27    37      31
## Normal       48    91      93
## High         23    51      73

CrossTable from the gmodels package does all these at once.

library(gmodels)
as.data.frame.matrix(Blood)
##        Under 30 30-49 Over 50
## Low          27    37      31
## Normal       48    91      93
## High         23    51      73
CrossTable(Blood, prop.t=TRUE, prop.r=TRUE, prop.c=TRUE)
## 
##  
##    Cell Contents
## |-------------------------|
## |                       N |
## | Chi-square contribution |
## |           N / Row Total |
## |           N / Col Total |
## |         N / Table Total |
## |-------------------------|
## 
##  
## Total Observations in Table:  474 
## 
##  
##              |  
##              |  Under 30 |     30-49 |   Over 50 | Row Total | 
## -------------|-----------|-----------|-----------|-----------|
##          Low |        27 |        37 |        31 |        95 | 
##              |     2.757 |     0.035 |     1.823 |           | 
##              |     0.284 |     0.389 |     0.326 |     0.200 | 
##              |     0.276 |     0.207 |     0.157 |           | 
##              |     0.057 |     0.078 |     0.065 |           | 
## -------------|-----------|-----------|-----------|-----------|
##       Normal |        48 |        91 |        93 |       232 | 
##              |     0.000 |     0.131 |     0.121 |           | 
##              |     0.207 |     0.392 |     0.401 |     0.489 | 
##              |     0.490 |     0.508 |     0.472 |           | 
##              |     0.101 |     0.192 |     0.196 |           | 
## -------------|-----------|-----------|-----------|-----------|
##         High |        23 |        51 |        73 |       147 | 
##              |     1.798 |     0.367 |     2.320 |           | 
##              |     0.156 |     0.347 |     0.497 |     0.310 | 
##              |     0.235 |     0.285 |     0.371 |           | 
##              |     0.049 |     0.108 |     0.154 |           | 
## -------------|-----------|-----------|-----------|-----------|
## Column Total |        98 |       179 |       197 |       474 | 
##              |     0.207 |     0.378 |     0.416 |           | 
## -------------|-----------|-----------|-----------|-----------|
## 
##
  1. MARGINAL DISTRUBUTION BLOOD PRESSURE IS 95,232,147
  2. CONDITIONAL DISTRUBUTION OF BLOOD PRESSURE UNDER 30’S IS 27,48,23
  3. CONDITIONAL DISTRUBUTION OF BLOOD PRESSURE FROM 30-49 IS 37, 91,51
  4. CONDITIONAL DISTRUBUTION OF BLOOD PRESSURE FOR 50+ IS 31,93,73
  5. YES, THIS DATA CLEARLY SHOWS TGAT THE OLDER YOU ARE, THE MORE LIKELY YOU ARE TO HAVE HIGH BLOOD PRESSURE. FOR EXAMPLE, 49% OF PEOPLE WITH HIGH BLOOD PRESSURE ARE ABOVE 50, WHILE ONLY 16% OF PEOPLE HAVE HIGH BLOOD PRESSURE WHILE BEING UNDER 30.

Some graphs…

barplot(prop.table(Blood,2), main = "Blood pressure by age group", xlab = "age group", col=c("green","blue", "magenta"))