Showing posts with label independent variables. Show all posts
Showing posts with label independent variables. Show all posts

Tuesday, December 11, 2012

Regression with Categorical Data

Introduction regression with categorical data:

In statistics, regression analysis includes any techniques for modeling and analyzing several variables, when the focus is on the relationship between a dependent variable and one or more independent variables. More specifically, regression analysis helps us understand how the typical value of the dependent variable changes when any one of the independent variables is varied, while the other independent variables are held fixed.

(Source: Wikipedia)

Regression with Categorical Data:

Definition regression with categorical data:

A categorical variable describe a exacting quality or characteristic. The data is divided into category and the information together is called categorical data

A categorical variable have a dimension scale consisting of a set of categories. For instance, political philosophy is often measured as liberal, moderate, or conservative. Diagnoses regarding breast cancer based on a mamma-gram use the categories normal, benign, probably benign, suspicious, and malignant.

The development of methods for categorical variables was stimulated by research studies in the social and biomedical sciences. Categorical scales are pervasive in the social sciences foe measuring attitudes and opinions. Categorical scales in biomedical sciences measure outcomes such as whether a medical treatment is successful. Understanding Prime Factors of 245 is always challenging for me but thanks to all math help websites to help me out.

Regression models involve the following variables:

The unknown parameters denoted as ß; this might be a scalar or a vector of length k.
The independent variable, X.
The dependent variable, Y.
A regression model relates Y to a function of X and ß.

Y ˜ f (X, ß)

Example Problem Regression with Categorical Data:

Probability of (X) is the probability that X is true. Probability of (X|Y) is the probability that X is true and given that Y is true.

Two hundred students of a class are classified according to the following 2 by 3 table. Where A, B, and C are mutually exclusive properties.

Status    Section A
Section B    Section C    Totals
Female    40      40    90    170
Male    50      20    20    90

Totals  90      60   110 260

Solution for comparing categorical data:

What is the probability that has chosen from the given table person as female?

P (F) = `170 / 260` = 65 %.

What is the probability that chosen person has section A?

P (A) = `90 / 260` = 35 %.

If chosen students are female, what is the probability that she has section B?

P (B|F) = `60 / 260` = 23 % = `(p(B and F)) / (p(F))` .

If chosen student has section C, what is the probability that the individual is a male?

P (M|C) = `20 / 110` = 18 %   = `(p(C and M))/ (p (C))` .

If chosen section has B or C, what is the probability that the student is a male?

P (M|B or C) = `20 /60` = 33 %.