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PullingMyHairOut3
10-27-2009, 06:06 PM
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
10-30-2009, 07:18 PM
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?