Question

According to researchers at Dan Jones & Associates, 1 in every 3 women has been a victim of domestic abuse (Domestic Violence: Incidence and Prevalence Study, Sept.–Dec., 2005). However, many experts on domestic violence believe that the proportion of women who are domestically abused is closer to p = .10. Compare the probability of observing 4 or more abused women in a sample of 15 if p = 1/3 and the probability of observing 4 or more abused women in a sample of 15 if p = .10. The results will lead us to believe that p=1/3 or p=.1? Group of answer choices p=1/3 p=.1

Answer 1

A) 79.08%

B) 5.55%

C)p = 1/3 is more appropriate than p = 0.1

Explanation:

This is a binomial probability distribution problem, so we will use the formula;

P(k) = (n!/(k!(n - k)!) × p^(k) × (1 - p)^(n-k)

We want to Compare the probability of observing 4 or more abused women in a sample of 15 if p = 1/3 = 0.3333 and the probability of observing 4 or more abused women in a sample of 15 if p = 0.10

Thus;

P(X ≥ 4) = P(4) + P(5) + P(6) + P(7) + P(8) + P(9) + P(10) + (P(11) + P(12) + P(13) + P(14) + P(15)

A) Thus at p = 0.3333;

P(4) = (15!/(4!(15 - 4)!) × 0.3333^(4) × (1 - 0.3333)^(15-4) = 0.1949

P(5) = (15!/(5!(15 - 5)!) × 0.3333^(5) × (1 - 0.3333)^(15-5) = 0.2143

Using online binomial probability calculator we can get the remaining values which are;

P(6) = 0.1786

P(7) = 0.1148

P(8) = 0.0574

P(9) = 0.0223

P(10) = 0.0067

P(11) = 0.0015

P(12) = 0.0003

P(13) = 0.0000

P(14) = 0.0000

P(15) = 0.0000

Thus;

P(X ≥ 4) = 0.1949 + 0.2143 + 0.1786 + 0.1148 + 0.0574 + 0.0223 + 0.0067 + 0.0015 + 0.0003 + 0 + 0 + 0 = 0.7908 = 79.08%

B) Now,for p = 0.1 and Using online binomial probability calculator, we have;

P(4) = 0.0428

P(5) = 0.0105

P(6) = 0.0019

P(7) = 0.0003

P(8) = 0.0000

P(9) = 0.0000

P(10) = 0.0000

P(11) = 0.0000

P(12) = 0.0000

P(13) = 0.0000

P(14) = 0.0000

P(15) = 0.0000

P(X ≥ 4) = 0.0428 + 0.0105 + 0.0019 + 0.0003 + 0.0000 + 0.0000 + 0.0000 + 0.0000 + 0.0000 + 0.0000 + 0.0000 + 0.0000 = 0.0555 = 5.55%

C) Comparing both Probabilities, 79.08% is far higher than 5.55%. Thus we can say that p = 1/3 is more appropriate than p = 0.1