Table 2.15 classifies a sample of psychiatric patients by their diagnosis and by whether their treatment prescribed drugs.

a. Conduct a test of independence, and interpret the P-value.

b. Obtain standardized residuals, and interpret.

c. Partition chi-squared into three components to describe differences and similarities among the diagnoses, by comparing (i) the first two rows, (ii) the third and fourth rows, (iii) the last rowto the first and second rows combined and the third and fourth rows combined.