Data for Exercise 1.53, 1.77, 1.88, 5.66, and 7.50

`Quail`

A data frame/tibble with 40 observations on two variables

- group
a character variable with values

`placebo`

and`treatment`

- level
low-density lipoprotein (LDL) cholestrol level

J. McKean, and T. Vidmar (1994), "A Comparison of Two Rank-Based Methods for the
Analysis of Linear Models," *The American Statistician, 48*, 220-229.

Kitchens, L. J. (2003) *Basic Statistics and Data Analysis*.
Pacific Grove, CA: Brooks/Cole, a division of Thomson Learning.