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Unformatted text preview: Student: Grady Silnonton Colu'se: 1\Iat11119: ElenIentaiy Statistics  Spring 3010  C‘RN: 49339 Instructor: Shawn Pan'ini  16 weeks
Date: 3."'18."'10 Book: T1‘iola: ElenIentaiy Statistics. Me
Time: 4:1? PM In a survey of 1100 people, 835 people said they voted in a recent presidential election. Voting records show that 23%
ofeligible voters actually did vote. Given that 73% of eligible voters actually did vote, (a) ﬁnd the probability that
among 1 100 randomly selected voters, at least 835 actually did vote. (b) What do the results from part (a) suggest? (a) Given n = l 100, p=0.'i'3, and q = 0.22, check that the values ofnp and nq are greater than or equal to 5. np = (1100x1173) nq = (1100x0279
803 29? Because both hp and nq have values greater than or equal to 5, the normal distribution can be used to approximate the
discrete binomial probability. Determine the values of u and o. u *5 up 6 c“ tnpq
(1100x073) = V11000.?3  0.2? 803 = 14.224 The probability of interest, P(x 2 835), is shown at
the right. Because normal probabilities are found for
areas to the left ofa speciﬁc value, calculate P(x 2 835)as 1 — P(x < 835). Because we are using a continuous distribution to approximate a discrete binomial probability, adjust x < 835 for
continuity. x < 835  0.5 = 834.5 Find the z score corresponding to x = 834.5. (x—u)
0 834.5  803 14.724
2.14 Approximate P(x < 835) , the area to the left of
834.5. P(x < 835) *5 P(z< 2.14)
= 0.9838 Page 1 Student: Grady Simonton Course: 1\Iat11119: Elementaiy Statistics  Spring 3010  C‘RN: 49339
Instructor: Shawn Pan'i11i  16 weeks
Date: 3."'18."'10 Book: T1‘iola: Elementaiy Statistics. Me Time: 4:1? PM Next ﬁnd P(x 2 835), the area to the right of 834.5. P(x 2 835) = l — P(x < 835)
1  0.9838
0.0162 (b) Interpret the probability. Since P(x 2 S35) is less than 5%, it is highly unlikely that at least 835 of l 100 people
actually voted. Page 3 ...
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This note was uploaded on 05/21/2010 for the course MATH 49239 taught by Professor Parvini during the Spring '10 term at Mesa CC.
 Spring '10
 PARVINI

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