Introduction
The chi-square test determines if there is an association between categorical variables.
Test of Independence
# Create contingency table
table_data <- table(df$var1, df$var2)
# Chi-square test
chisq.test(table_data)
# With correction
chisq.test(table_data, correct = TRUE)
Goodness of Fit
# Observed counts
observed <- c(10, 20, 30)
# Expected proportions
expected <- c(0.25, 0.25, 0.5)
chisq.test(observed, p = expected)
Expected Frequencies
# Get expected values
result <- chisq.test(table_data)
result$expected
Effect Size
# Cramer's V
library(vcd)
assocstats(table_data)
Summary
Chi-square tests categorical associations. Check expected frequencies assumption.