Sodium Content of Water

An independent agency measures the sodium content in 20 samples from source X and in 10 samples from source Y and stores them in data frame Water. Data are used in Example 9.12.

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

Source

Ugarte, M. D., Militino, A. F., and Arnholt, A. T. (2008) Probability and Statistics with R. Chapman & Hall/CRC.

Examples

with(data = Water,
t.test(X, Y, alternative = "less"))
#> 
#> 	Welch Two Sample t-test
#> 
#> data:  X and Y
#> 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 of x mean of y 
#>      76.4      81.2 
#>