Data for Example 7.20

Stress

Format

A data frame/tibble with 12 observations on two variables

prestress

short term memory score before being exposed to a stressful situation

poststress

short term memory score after being exposed to a stressful situation

References

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

Examples


diff <- Stress$prestress - Stress$poststress
qqnorm(diff)
qqline(diff)

t.test(diff)
#> 
#> 	One Sample t-test
#> 
#> data:  diff
#> t = 2.6018, df = 11, p-value = 0.02462
#> alternative hypothesis: true mean is not equal to 0
#> 95 percent confidence interval:
#>  0.2053928 2.4612738
#> sample estimates:
#> mean of x 
#>  1.333333 
#> 
t.test(Stress$prestress, Stress$poststress, paired = TRUE)
#> 
#> 	Paired t-test
#> 
#> data:  Stress$prestress and Stress$poststress
#> t = 2.6018, df = 11, p-value = 0.02462
#> alternative hypothesis: true difference in means is not equal to 0
#> 95 percent confidence interval:
#>  0.2053928 2.4612738
#> sample estimates:
#> mean of the differences 
#>                1.333333 
#> 
if (FALSE) {
wilcox.test(Stress$prestress, Stress$poststress, paired = TRUE)
}