lecture_04

lecture_04 - Two-Way Contingency Tables Contingency Tables...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Two-Way Contingency Tables
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
    Contingency Tables -  Introduction Contingency tables are common ways to  summarize categorical / qualitative data. Cells of the table contain frequency counts of  outcomes. In other words contingency table is a  table of counts. A simplest form of contingency table is a     2 x 2 table.
Background image of page 2
  Contingency Tables -  Introduction A two-dimensional contingency table is formed by  classifying subjects by two variables. One variable determines the row categories, the other  variable defines the column categories. The combination of row and column categories are called  cells. Examples include classifying subjects by sex (male/female)  and smoking status (current/former/never) or by classifying  subjects by smoking status (yes/no) and whether the person  has a CHD (yes/no).
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
      2 x 2 Contingency Table Example: Following table classifies a sample of 1091 Americans who were asked for their belief in  afterlife.  Gender Yes No or Undecided Females 435 147 Males 374 134
Background image of page 4
2 x 2 Contingency Table                              Belief in Afterlife Gender Yes No or Undecided Females 435 147 Males 374 134 In the above example there are 2 categorical variables: GENDER Female, Male BELIEF – Yes, No There are 2 rows and 2 columns. Therefore it is a 2 x 2 table.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
      Objective of contingency tables Objective is to see if there is an association  between the categorical variables. In addition, we may be interested in the strength of  the association. For the “Belief in Afterlife” example: Is one sex more likely than the other to believe in  afterlife? Is belief in afterlife independent of  gender?
Background image of page 6
            Example 2   Categorizing patients by their favorable or unfavorable  response to two different drugs. The objective is to see if there is any association between drugs  and their favourable outcomes. Is drug A more favourable than drug B? Drug Favorable Unfavorable A 16 48 B 40 20
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
        Example 3  Death sentence by race of defendant for 147 penalty trials. The objective is to see if there is any association between  death sentence and race of the defendant. Is death sentence more likely for a black than life sentence? Blacks Nonblacks DEATH 28 22 LIFE 45 52
Background image of page 8
    Probability Structure Categorical data consist of frequency counts of  observations occurring in the response categories.  Let X and Y denote two categorical variables X having I  levels and Y having J levels.  We can have the IJ possible combinations of outcomes in a  rectangular table having I rows for the categories of X and  columns for the categories of Y. The cells of the table  represent the IJ possible outcomes. 
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/28/2007 for the course BTRY 6030 taught by Professor Das,t. during the Spring '06 term at Cornell.

Page1 / 40

lecture_04 - Two-Way Contingency Tables Contingency Tables...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online