14.2 Example: Clinical Trial

library(lsr)
clin.trial <- readRDS("data/clintrial.rds")
str(clin.trial)

## 'data.frame':    18 obs. of  3 variables:
##  $ drug     : Factor w/ 3 levels "placebo","anxifree",..: 1 1 1 2 2 2 3 3 3 1 ...
##  $ therapy  : Factor w/ 2 levels "no.therapy","CBT": 1 1 1 1 1 1 1 1 1 2 ...
##  $ mood.gain: num  0.5 0.3 0.1 0.6 0.4 0.2 1.4 1.7 1.3 0.6 ...

clin.trial

##        drug    therapy mood.gain
## 1   placebo no.therapy       0.5
## 2   placebo no.therapy       0.3
## 3   placebo no.therapy       0.1
## 4  anxifree no.therapy       0.6
## 5  anxifree no.therapy       0.4
## 6  anxifree no.therapy       0.2
## 7  joyzepam no.therapy       1.4
## 8  joyzepam no.therapy       1.7
## 9  joyzepam no.therapy       1.3
## 10  placebo        CBT       0.6
## 11  placebo        CBT       0.9
## 12  placebo        CBT       0.3
## 13 anxifree        CBT       1.1
## 14 anxifree        CBT       0.8
## 15 anxifree        CBT       1.2
## 16 joyzepam        CBT       1.8
## 17 joyzepam        CBT       1.3
## 18 joyzepam        CBT       1.4

We look at the effect of drug on mood.gain

library(tidyverse)
clin.trial%>%
  group_by(drug)%>%
  reframe(avg_mood.gain=mean(mood.gain),
          sd_mood.gain=sd(mood.gain))

## # A tibble: 3 × 3
##   drug     avg_mood.gain sd_mood.gain
##   <fct>            <dbl>        <dbl>
## 1 placebo          0.45         0.281
## 2 anxifree         0.717        0.392
## 3 joyzepam         1.48         0.214

gplots::plotmeans(formula = mood.gain ~ drug,  # plot mood.gain by drug
             data = clin.trial,           # the data frame
             xlab = "Drug Administered",  # x-axis label
             ylab = "Mood Gain",          # y-axis label
             n.label = FALSE  )