Percent of vehicles passing inspection by type inspection station

Data for Exercise 8.59

Inspect

Format

A data frame/tibble with 174 observations on two variables

station

a factor with levels auto inspection, auto repair, car care center, gas station, new car dealer, and tire store

passed

a factor with levels less than 70%, between 70% and 84%, and more than 85%

Source

The Charlotte Observer, December 13, 1992.

References

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

Examples

T1 <- xtabs(~ station + passed, data = Inspect)
T1
#>                  passed
#> station           less than 70% between 70% and 84% more than 85%
#>   auto inspection             1                   8             4
#>   auto repair                16                  13             7
#>   tire store                 16                  11             6
#>   gas station                19                  21             6
#>   car care center             4                   4             4
#>   new car dealer              1                   5            28
barplot(T1, beside = TRUE, legend = TRUE)

chisq.test(T1)
#> Warning: Chi-squared approximation may be incorrect
#> 
#> 	Pearson's Chi-squared test
#> 
#> data:  T1
#> X-squared = 61.027, df = 10, p-value = 2.316e-09
#> 
rm(T1)

if (FALSE) {
library(ggplot2)
ggplot2::ggplot(data = Inspect, aes(x = passed, fill = station)) + 
           geom_bar(position = "dodge") + 
           theme_bw()
}