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About: Random Selection

Module by: Paul E Pfeiffer. E-mail the author

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Name: Random Selection
ID: m23652
Language: English (en)
Summary: The usual treatments deal with a single random variable or a fixed, finite number of random variables, considered jointly. However, there are many common applications in which we select at random a member of a class of random variables and observe its value, or select a random number of random variables and obtain some function of those selected. This is formulated with the aid of a counting or selecting random variable N, which is nonegative, integer valued. It may be independent of the class selected, or may be related in some sequential way to members of the class. We consider only the independent case. Many important problems require optional random variables, sometimes called Markov times. These involve more theory than we develop in this treatment. As a basic model, we consider the sum of a random number of members of an iid class. In order to have a concrete interpretation to help visualize the formal patterns, we think of the demand of a random number of customers. We suppose the number of customers N is independent of the individual demands. We formulate a model to be used for a variety of applications. Under standard independence conditions, we obtain expressions for compound demand D, conditional expectation for g(D) given N = n, and moment generating function for D. These are applied in various situations.
Subject: Mathematics and Statistics
Keywords: Basic sequence, Compound demand, Counting random variable, Counting random variables, Incremental sequence, Matlab and compound demand, Random sums
License: Creative Commons Attribution License CC-BY 3.0
Authors: Paul E Pfeiffer (perhp@earthlink.net)
Copyright Holders: Paul E Pfeiffer (perhp@earthlink.net)
Maintainers: Paul E Pfeiffer (perhp@earthlink.net), Daniel Williamson (dcwill@cnx.org), C. Sidney Burrus (csb@rice.edu)
Latest version: 1.6 (history)
First publication date: Apr 17, 2009 5:24 pm -0500
Last revision to module: Sep 18, 2009 1:46 pm -0500

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Version History

Version: 1.6 Sep 18, 2009 1:46 pm -0500 by Daniel Williamson
Changes: 
added google analytics tracking code
Version: 1.5 Jul 27, 2009 12:11 pm -0500 by Daniel Williamson
Changes: 
disjoint union fix
Version: 1.4 Jun 19, 2009 11:23 am -0500 by Daniel Williamson
Changes: 
m-file fixes, supplemental links, metadata updated
Version: 1.3 Jun 9, 2009 5:20 pm -0500 by Daniel Williamson
Changes: 
updated links, images and accessibility
Version: 1.2 May 26, 2009 4:44 pm -0500 by Daniel Williamson
Changes: 
fixed module names, and updated content structure
Version: 1.1 May 20, 2009 1:00 pm -0500 by Paul E Pfeiffer
Changes: 
Content

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American Chemical Society (ACS) Style Guide:

Pfeiffer, P. Random Selection, Connexions Web site. http://cnx.org/content/m23652/1.6/, Sep 18, 2009.

American Medical Assocation (AMA) Manual of Style:

Pfeiffer P. Random Selection [Connexions Web site]. September 18, 2009. Available at: http://cnx.org/content/m23652/1.6/.

American Psychological Assocation (APA) Publication Manual:

Pfeiffer, P. (2009, September 18). Random Selection. Retrieved from the Connexions Web site: http://cnx.org/content/m23652/1.6/

Chicago Manual of Style (Bibliography):

Pfeiffer, Paul. "Random Selection." Connexions. September 18, 2009. http://cnx.org/content/m23652/1.6/.

Chicago Manual of Style (Note):

Paul Pfeiffer, "Random Selection," Connexions, September 18, 2009, http://cnx.org/content/m23652/1.6/.

Chicago Manual of Style (Reference, in Author-Date style):

Pfeiffer, P. 2009. Random Selection. Connexions, September 18, 2009. http://cnx.org/content/m23652/1.6/.

Modern Languages Association (MLA) Style Manual:

Pfeiffer, Paul. Random Selection. Connexions. 18 Sep. 2009 <http://cnx.org/content/m23652/1.6/>.