# What is the mean and variance of X?

Six Sigma – iSixSigma Forums Old Forums General What is the mean and variance of X?

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• #51818

Tig
Member

I am double checking my work.
Does nay one know what the following would be?
In a survey,85% of voters support referendum.If 10 voters are chosen at random,and X is the number of voters that support this referendum, find the mean and variance of X?

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#180834

Van Loon
Participant

X~B(n,p)
E(X)=np
V(X)=npq

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#180835

Tig
Member

In a survey,85% of voters support referendum.If 10 voters are chosen at random,and X is the number of voters that support this referendum, find the mean and variance of X?

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#180837

Darth
Participant

TIG, START DOING YOUR OWN HOMEWORK AND STOP POSTING YOUR HOMEWORK QUESTIONS HERE!! THERE IS SOMETHING INHERENTLY DISHONEST ABOUT HAVING OTHERS DO YOUR HOMEWORK. START STUDYING!!!!!

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#180839

Tig
Member

I already did it. I was just checking to see if I am correct.

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#180841

Darth
Participant

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#180845

Helper
Participant

The binomial distribution has the following properties:

The mean of the distribution (ìx) is equal to n * P .
The variance (ó2x) is n * P * ( 1 – P ).
The standard deviation (óx) is sqrt[ n * P * ( 1 – P ) ].

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#180846

Tig
Member

I do not think this was correct. Is there another one you would like me to post my answer to?
I never had statistics in my life and this is only my 4 time in the class
so I would like to know I am on the right page.
I have no one to help me so that is why I was looking for help. I think I am in wrong place.

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#180848

Darth
Participant

I don’t mean to be harsh with you and I feel badly that you may not have resources where ever you are but if we answered ever post from a student not able to do his/her homework this site would be full of such things. This site was founded to exchange information regarding Lean Six Sigma and not as a tutoring site for students. Here is the stated purpose of the Forum:This discussion forum covers the full range of Six Sigma Quality discourse and provides a fascinating look at evolving viewpoints, debate and advice on every subject from performing a 2 sample t-test to leading a Six Sigma deployment.

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#180849

Darth
Participant

And yes, according to the help provided by Helper, your answer is correct.

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