In an analysis of preliminary test results from XSORT gender-selection method, 1

Question

In an analysis of preliminary test results from XSORT gender-selection method, 14 babies are born and it is assumed that 50% of babies are girls, so n = 14 and p = 0.5. Find the mu (mean), sigma (standard deviation), the minimum usual value and the maximum usual value. mu = sigma = mu - 2 sigma = mu + 2 sigma = Would it be unusual to find exactly 12 of the babies to be girls? Ina Gallup poll of 1013 randomly selected adults, 66% said that they worry about identity theft, so n = 1013 and p = 0.66. Find the mu (mean), sigma (standard deviation), the minimum usual value and the maximum usual value. mu = sigma = mu - 2 sigma = mu + 2 sigma = Would it be unusual to identify only 650 people concerned with identity theft? ____________

Explanation / Answer

3.

In a binomial dist,

Mean = np,

stdev= sqrt(np*p')

a. Mu = np = .5*14 = 7

b. Sigma = sqrt(npq) = sqrt(7*.5) = 1.87

c. Mu-2sigma = 7-2*1.87 = 3.26

d. Mu+2sigma = 7+2*1.87 = 10.74

e. Since 12 does not lies between 3.26 and 10.74 that means that the probability to find exactly 12 babies is unusual.

This is because 12 lies easily outside the 95% confidence interval. if it were to lie inside the 95% CI then event would

not have been rare.

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