Data for Example 7.15

Drug

Format

A data frame/tibble with 28 observations on two variables

trials

number of trials to master a task

group

a factor with levels control and experimental

References

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

Examples


boxplot(trials ~ group, data = Drug,
        main = "Example 7.15", col = c("yellow", "red"))

wilcox.test(trials ~ group, data = Drug)
#> Warning: cannot compute exact p-value with ties
#> 
#> 	Wilcoxon rank sum test with continuity correction
#> 
#> data:  trials by group
#> W = 47.5, p-value = 0.02213
#> alternative hypothesis: true location shift is not equal to 0
#> 
t.test(rank(trials) ~ group, data = Drug, var.equal = TRUE)
#> 
#> 	Two Sample t-test
#> 
#> data:  rank(trials) by group
#> t = -2.5323, df = 26, p-value = 0.01771
#> alternative hypothesis: true difference in means is not equal to 0
#> 95 percent confidence interval:
#>  -13.007341  -1.351633
#> sample estimates:
#>      mean in group control mean in group experimental 
#>                   11.16667                   18.34615 
#>