* do-file for Exercise 27.8 of PSLS 3e
version 17 /* works also with versions 13-16 */

import delimited "R:\Chapter 27\ex27_008.csv"
keep if weeds==0 | weeds==9

* ranksum command for Mann-Whitney-Wilcoxon 2-sample test (or Wilcoxon rank sum test)
ranksum yield, by(weeds)
ttest yield, by(weeds) unequal welch

* analyses without outlier
ranksum yield if yield>150, by(weeds)
ttest yield if yield>150, by(weeds) unequal welch