Section 4-3 Relations in Categorical Data Statistics 101 Section 4-3 Relations in Categorical Data

Categorical Data Typically grouped into categories Examples are age, education, etc.

Example 4.19 p 241

Marginal Distributions On the previous example – education and age are called marginal distributions because their totals appear at the right and bottom margins of the two-way table. http://www.youtube.com/watch?v=_b2RMV0Pz68 Percents are more informative than counts.

Bar-graph of years of schooling completed among people aged 25 years and over

How common is college education? What do you think?

What do you see

Conditional Distributions Useful when the column variable is the explanatory variable. There is a conditional distribution of the row variable for each column in the table http://www.youtube.com/watch?v=-vLW7Ss7M94

Example of Conditional Distribution

Simpson’s Paradox The reversal of the direction of a comparison or an association when data from several groups are combined to form a single group. http://www.youtube.com/watch?v=wgLUDw8eLB4

To understand this paradox Read through example 4.13 on p 249 entitled ‘patient outcomes in hospitals’