Difference between revisions of "SOCR EduMaterials Activities Binomial PGF"

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(New page: == This is an activity to explore the Probability Generating Functions for the Bernoulli, Binomial, Geometric and Negative-Binomial Distributions.== * '''Description''': You can access t...)
 
(See also)
 
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== This is an activity to explore the Probability Generating Functions for the Bernoulli, Binomial, Geometric and Negative-Binomial Distributions.==
 
== This is an activity to explore the Probability Generating Functions for the Bernoulli, Binomial, Geometric and Negative-Binomial Distributions.==
  
* '''Description''':  You can access the applets for the above distributions at  http://www.socr.ucla.edu/htmls/SOCR_DistributionFunctors.html .  
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* '''Description''':  You can access the applets for the above distributions at  http://socr.umich.edu/html/dist/ .  
  
 
* '''Exercise 1:''' Use SOCR to graph the PGF's and print the following distributions and answer the questions below.  Also, comment on the shape of each one of these distributions:
 
* '''Exercise 1:''' Use SOCR to graph the PGF's and print the following distributions and answer the questions below.  Also, comment on the shape of each one of these distributions:
**a.<math> X \sim Bernoulli(0.5) </math>
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**a.<math> X \sim Bernoulli(0.1) </math>
**b.<math> X \sim Binomial(1,0.5) </math>
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**b.<math> X \sim Binomial(10,0.9) </math>
**c.<math> X \sim Geometric(0.5) </math>
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**c.<math> X \sim Geometric(0.3) </math>
**d.<math> X \sim NegativeBinomial(1, 0.5) </math>
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**d.<math> X \sim NegativeBinomial(10, 0.7) </math>
  
 
Below you can see a snapshot of the PGF of the distribution of <math> X \sim Bernoulli(0.8) </math>
 
Below you can see a snapshot of the PGF of the distribution of <math> X \sim Bernoulli(0.8) </math>
<center>[[Image:BernoulliPGF.jpg|600px]]</center>
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<center>[[Image:BernoulliPGF1.jpg|600px]]</center>
  
 
Do you notice any similarities between the graphs of these PGF's between any of these distributions?
 
Do you notice any similarities between the graphs of these PGF's between any of these distributions?
  
* '''Exercise 2:''' Use SOCR to graph and print the PGF of the distribution of a geometric random variable with <math> p=0.2,  p=0.7 </math>.  What is the shape of this function?  What happens when <math> p </math> is large?  What happens when <math> p </math> is small?
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* '''Exercise 2:''' Use SOCR to graph and print the PGF of the distribution of a geometric random variable with <math> p=0.1,  p=0.8 </math>.  What is the shape of this function?  What happens when <math> p </math> is large?  What happens when <math> p </math> is small?
  
 
* '''Exercise 3:''' You learned in class about the properties of PGF's If <math> X_1, ...X_n</math> are iid. and <math>Y = \sum_{i=1}^n X_i. </math> then <math>P_{y}(t) = {[P_{X_1}(t)]}^n</math>.
 
* '''Exercise 3:''' You learned in class about the properties of PGF's If <math> X_1, ...X_n</math> are iid. and <math>Y = \sum_{i=1}^n X_i. </math> then <math>P_{y}(t) = {[P_{X_1}(t)]}^n</math>.
**a. Show that the PGF of the sum of <math>n</math> independent Bernoulli Trials with success probability <math> p </math> is the same as the MGF of the Binomial Distribution using the corollary above.  
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**a. Show that the PGF of the sum of <math>n</math> independent Bernoulli Trials with success probability <math> p </math> is the same as the PGF of the Binomial Distribution using the corollary above.  
 
**b. Show that the PGF of the sum of <math>n</math> independent Geometric Random Variables with success probability <math> p </math> is the same as the MGF of the Negative-Binomial Distribution using the corollary above.  
 
**b. Show that the PGF of the sum of <math>n</math> independent Geometric Random Variables with success probability <math> p </math> is the same as the MGF of the Negative-Binomial Distribution using the corollary above.  
**c.  How does this relate to Exercise 1?  Does having the same MGF mean they are distributed the same?
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**c.  How does this relate to Exercise 1?  Does having the same PGF mean they are distributed the same?
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* '''Exercise 4:'''  Suppose that X has a pgf <math> P_{x}(t)=(1-p)+pt </math> and let <math> Y = aX + b.</math>  What is <math> P_{y}(t) </math> ?
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==See also==
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* [[SOCR_EduMaterials_FunctorActivities_PGF | Other SOCR Distribution Functor Activities]]
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<hr>
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* SOCR Home page: http://www.socr.umich.edu
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{{translate|pageName=http://wiki.socr.umich.edu/index.php?title=SOCR_EduMaterials_Activities_Binomial_PGF}}

Latest revision as of 09:55, 5 March 2014

This is an activity to explore the Probability Generating Functions for the Bernoulli, Binomial, Geometric and Negative-Binomial Distributions.

  • Exercise 1: Use SOCR to graph the PGF's and print the following distributions and answer the questions below. Also, comment on the shape of each one of these distributions:
    • a.\( X \sim Bernoulli(0.1) \)
    • b.\( X \sim Binomial(10,0.9) \)
    • c.\( X \sim Geometric(0.3) \)
    • d.\( X \sim NegativeBinomial(10, 0.7) \)

Below you can see a snapshot of the PGF of the distribution of \( X \sim Bernoulli(0.8) \)

Error creating thumbnail: File missing

Do you notice any similarities between the graphs of these PGF's between any of these distributions?

  • Exercise 2: Use SOCR to graph and print the PGF of the distribution of a geometric random variable with \( p=0.1, p=0.8 \). What is the shape of this function? What happens when \( p \) is large? What happens when \( p \) is small?
  • Exercise 3: You learned in class about the properties of PGF's If \( X_1, ...X_n\) are iid. and \(Y = \sum_{i=1}^n X_i. \) then \(P_{y}(t) = {[P_{X_1}(t)]}^n\).
    • a. Show that the PGF of the sum of \(n\) independent Bernoulli Trials with success probability \( p \) is the same as the PGF of the Binomial Distribution using the corollary above.
    • b. Show that the PGF of the sum of \(n\) independent Geometric Random Variables with success probability \( p \) is the same as the MGF of the Negative-Binomial Distribution using the corollary above.
    • c. How does this relate to Exercise 1? Does having the same PGF mean they are distributed the same?
  • Exercise 4: Suppose that X has a pgf \( P_{x}(t)=(1-p)+pt \) and let \( Y = aX + b.\) What is \( P_{y}(t) \) ?

See also




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