properties of the binomial distribution question

PullingMyHairOut3

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Joined
Oct 27, 2009
Messages
1
Is this right? I am totally confused! My friend tried to help me and this is what we got. He told me about this forum and said maybe you could help.

Long-term history has shown that 25% of all elected offices in a rural county have been won by Democratic candidates. This year there are 4 offices up for public election in the county. Let a “success” correspond to a Democratic being elected to public office in the county and X = the number of Democrats that have been elected out of the 4 offices that were up for election.

1) What are the values of n, p, and q?

n = 4 p = 0.25 q = 0.75

2) What are the possible outcomes for the random variable X? List them in the table below.

x
--------
0
1
2
3
4

3) Using what you know about the binomial distribution and Table 3, complete the second column to create a probability distribution table.

p(x)
---------
0.316406
0.421875
0.210938
0.046875
0.003906

or do I round them for this column to equal "1"?

p(x)
----------
0.3164
0.4219
0.2109
0.0469
0.0039

4) What is the expected number of Democrats who will win office in the coming election?

n(4) x p(0.25) = 1

5) What is the standard deviation of r?

? 4x0.25x0.75 = 0.75
? 0.75 = 0.8660254037844386 = 0.866
 

tkhunny

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Apr 12, 2005
Messages
9,790
Rounding? Who cares? Get the right values first. You did that. Worry about rounding specific to your applciation.

You have it all. Why do you doubt?
 
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