3.3 Measurement: Contingency tables

• Discussion
  1. Q: What do the tables show (start with Table 3.3 then 3.4)?
  2. Q: What does a cell in those tables show?
  3. Q: What would the univariate distribution for income look like behind Table 3.4?
  4. Q: What is a missing value/NA? Do they appear in Table 3.3 and 3.4?
  5. Q: How would the data underlying Table 3.3 and 3.4 look like in a dataframe?

Table 3.3: Contingency table of discipline (this class)

Economics	Sociology
4	7

Table 3.4: Contingency table of Income/Gender

	female	male
high income	5	0
low income	2	3

Notes

• Lessons to be learned
  • We can conceptualize data as units that have been assigned to cells through observation. Each cell represents a particular value on the variable (or a combination of values on several variables).
  • “A contingency table (also known as a cross tabulation or crosstab) is a type of table in a matrix format that displays the (multivariate) frequency distribution of the variables.” (Wikipedia)
    • Displays how observations are distributed across the values of our variable(s).
  • Contingency tables are “underused”.
  • Ideally, display contingency tables with the missings (in R).