Weight of chickens

Data from a randomized blocked experiment to investigate the effect of a drug added to the feed of chicks in an attempt to promote growth. The comparison is between three treatments: standard feed (control), standard feed plus low dose of drug, standard feed plus high dose of drug. The experimental unit is a group of chicks, reared and fed together in the birdhouse. The experimental units are grouped three to a block, with physically adjacent units going in the same block.

Usage

chickens

Format

A data frame with 24 rows and 3 columns:

block

Block corresponding to a bird house

dose

Dose of drug added to the diet (`control`, `low` or `high`)

weight

Average weight per bird (in pounds) at maturity for the group of birds in each experimental unit

Source

Snee, R.D. (1985) Graphical display of results of three-treatment randomized block experiments. Applied Statistics, 34, 71-7.

Examples

library(hsds)
library(ggplot2)
#> Error in library(ggplot2): there is no package called ‘ggplot2’
library(lme4)
#> Error in library(lme4): there is no package called ‘lme4’

# Plot of the average weight per diet, on top of a box plot
ggplot(chickens, aes(x = dose, y = weight)) +
  geom_boxplot(color = "gray") +
  geom_line(aes(color = block, group = block)) +
  geom_point(aes(color = block), size = 2) +
  theme_classic()
#> Error in ggplot(chickens, aes(x = dose, y = weight)): could not find function "ggplot"

# Model of the weight by dose, taking into account the random variation within
# each individual unit
mod <- lmer(weight ~ dose + (1 | block), data = chickens)
#> Error in lmer(weight ~ dose + (1 | block), data = chickens): could not find function "lmer"
summary(mod)
#> Error in eval(expr, envir, enclos): object 'mod' not found

# The `modelbased` package is great to estimate marginal means
modelbased::estimate_means(mod, at = c("dose"))
#> Error in loadNamespace(x): there is no package called ‘modelbased’

# Or to estimate contrasts to see if there is a significant difference in weight
# between diets
modelbased::estimate_contrasts(mod, contrast = "dose", p_adjust = "tukey")
#> Error in loadNamespace(x): there is no package called ‘modelbased’