19. Of 75 voters, 30 claimed to be independent. Which of the following represent

Question

19. Of 75 voters, 30 claimed to be independent. Which of the following represents a 90 percent confidence interval for the proportion of all voters who are independent?

Select one:

a. [0.307, 0.493]

b. [0.517, 0.845]

c. [0.139, 0.732]

d. [0.681, 0.899]

37. The mean arrival rate of flights at O’Hare Airport is 195 flights per hour with a historical standard deviation of 13 flights. A new air traffic control procedure is implemented. In the next 30 days, the mean arrival rate is 200 flights per hour. Has there been a significant change in the mean number of arrivals per hour at the 5% level of significance?

Select one:

a. Yes

b. No

c. Cannot be determined

d. None of these

38. The mean arrival rate of flights at O’Hare Airport is 195 flights per hour with a historical standard deviation of 13 flights. A new air traffic control procedure is implemented. In the next 30 days, the mean arrival rate is 200 flights per hour. Has there been a significant change in the mean number of arrivals per hour at the 1% level of significance?

Select one:

a. No

b. Cannot be determined

c. Yes

d. None of these

Explanation / Answer

19)

given that of 75 voters, 30 claimed to be independent

sample size i.e n = 75

sample proportion of independent voters i.e p = 30/75 = 0.4

standard deviation of proportion of all voters who are independent i.e p= [p*(1-p)/n]0.5 = [0.4*(1-0.4)/75]0.5

= 0.057

we know that 90% CI of normal distribution is (mean-1.645*sd, mean+1.645*sd)

so 90 percent confidence interval for the proportion of all voters who are independent is (0.4-1.645*0.057, 0.4+1.645*0.057) i.e (0.307, 0.493)

so answer is (a)

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