Binomial, Geometric and Poisson distributions in excel

B. Heard(Not to be posted, used, etc. without

my permission, students may download one copy for personal use)

Binomial, Geometric and Poisson Distributions in Excel

Binomial, Geometric and Poisson Distributions with Excel

What I am about to show you, will amaze you.

However…If your instructor has told you that you MUST

use Minitab, I can’t change that requirementYou could still use these “Magic Calculators”

to check your work.I think it is important for you to be familiar

with Excel, since that is what you have access to in the work environment (Microsoft Excel)


Before we start, follow these instructions carefullyGo to

http://highered.mcgraw-hill.com/sites/0070620164/student_view0/excel_templates.html

A picture follows on the next page



This is what it should look like, it is a long page, I couldn’t capture it all…


Now click on the link that says “Binomial”Choose/Click “Open”

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1


When it opens, click on the “Review” tab and then click “Unprotect Sheet” – You must do this step

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We a r e “ u n p r o t e c t i n g ” t h e s h e e t s o w e c a n i n p u t o u r o n v a l u e s .


Now save your Excel Workbook file as something like “Binomial_Calculator”

Let’s finish setting up our calculators


Now go back to the webpage


Now click on the link that says “Geometric”Choose/Click “Open”

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1


When it opens, click on the “Review” tab and then click “Unprotect Sheet”

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Now save your Excel Workbook file as something like “Geometric_Calculator”

We need to add one more


Now go back to the webpage


Now click on the link that says “Poisson”Choose/Click “Open”

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When it opens, click on the “Review” tab and then click “Unprotect Sheet”

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Now save your Excel Workbook file as something like “Poisson_Calculator”

Let’s use our new calculators now


Binomial Distribution Example


, Example 2, a binomial


Open your Excel File “Binomial_Calculator”Input 3 for n and 0.75 for p and hit ENTER

Don’t forget to hit the enter

key after inputting


IMPORTANTDON’T FORGET TO HIT THE ENTER KEY OR

CLICK ON ANOTHER CELL AFTER YOU INPUT YOUR VALUE

DO NOT MESS WITH THE REST OF THE SHEET, ONLY INPUT INTO GREEN CELLS I NOTE, YOU WILL HAVE TO DOWNLOAD IT AGAIN IF YOU INADVERTENTLY CHANGE A CELL THAT IS USED FOR CALCULATIONS


The probability of exactly 2 is to the right of 2 under the P(exactly x) columnCheck the book, we nailed it! Our answer is 0.4219. they noted 0.422 (they just rounded)

Note this calculator also gives me the mean, variance and standard deviation of the binomial with an n of 3 and p of 0.75


Geometric Distribution Example


, Example 1, a geometric


Open your Excel File “Geometric_Calculator”

Input 0.74 for p and hit ENTER

Don’t forget to hit the enter

key after inputting!!!!!!


The question was to find the probability that he hits his first free throw on the third or fourth attempt so we have to add the results for exactly 3 and exactly 4 which is 0.0500 + 0.0130 = 0.0630Again we nailed it!Note you are given the mean, variance and standard deviation of a geometric distribution with p = 0.74 above also.


Poisson Distribution Example


, Example 3, a Poisson example (It is pronounced “Poy-zahn”)


Open your Excel File “Poisson_Calculator”Input 3.6 for the Mean and hit ENTER


The question was to find the probability that 7 rabbits would be found (based on a Poisson distribution with an average of 3.6) Look to the right of 7 and under P(Exactly x) to see 0.0425 is the answer.Nailed it!Note you are given the variance and standard deviation of a Poisson distribution with Mean = 3.6 above also. What is the Mean? You input it! It’s 3.6, note the Variance = Mean on a Poisson distribution and the standard deviation is just the square root of that number.


The P(At most x) and P(At least x) are very valuable also. Let’s take a look at the last problem again where we were looking for rabbits (Poisson) in a field where an average of 3.6 rabbits/acre were living.


To the right of 4 and under P(At most x) would give us the answer to a question that could be asked a couple of ways:

What is the probability that no more than 4 rabbits were living on a given acre? 0.7064

What is the probability that less than 5 ( P(x<5) ) rabbits were living on a given acre? 0.7064

Basically it gives us P(x≤4) or P(x<5)


To the right of 6 and under P(At least x) would give us the answer to a question that could be asked a couple of ways:

What is the probability that more than 5 rabbits ( P(x>5) ) were living on a given acre? 0.0733

What is the probability that at least 6 rabbits were living on a given acre? 0.0733

Basically it gives us P(x≥6) or P(x>5)

BASED ON THE MEAN WE INPUT


Good luck, I hope this helps.If you enjoy reading the humor of an absent

minded math professor, come be a fan at www.facebook.com/cranksmytractor or visit me at www.CranksMyTractor.com where I write about everyday things I come across…

My best to you all…

“Statistics do not lie, but people do.”


http://www.facebook.com/cranksmytractor

http://www.cranksmytractor.com/

Binomial, Geometric and Poisson distributions in excel

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