Sodium Content of Water

Source: R/AgainStart.R

An independent agency measures the sodium content in 20 samples from source x and in 10 samples from source y and stores them in the data frame WATER.

WATER

Format

A data frame with 30 observations on the following 4 variables:

  • x (sodium content measured in mg/L)

  • y (sodium content measured in mg/L)

  • sodium (combined sodium content measured in mg/L)

  • source (a factor with levels x and y)

References

Ugarte, M. D., Militino, A. F., and Arnholt, A. T. 2015. Probability and Statistics with R, Second Edition. Chapman & Hall / CRC.

Examples

ggplot(data = WATER, aes(x = sodium, y = ..density.., fill = source)) + 
geom_density(alpha = 0.2)

t.test(sodium ~ source, data = WATER, alternative = "less")
#> 
#> 	Welch Two Sample t-test
#> 
#> data:  sodium by source
#> t = -1.8589, df = 22.069, p-value = 0.03822
#> alternative hypothesis: true difference in means is less than 0
#> 95 percent confidence interval:
#>        -Inf -0.3665724
#> sample estimates:
#> mean in group x mean in group y 
#>            76.4            81.2 
#>