400 adults from the East, 400 Adults who say that traffic congestion is a seriou

Question

400 adults from the East,400

Adults who say that traffic congestion is a serious problem

EastEast

36%

SouthSouth

33%

MidwestMidwest

25%

WestWest

56%

(a) Construct a 99% confidence interval for the proportion of adults from the MidwestMidwest

who say traffic congestion is a serious problem.The 99% confidence interval for the proportion of adults from the Midwest who say traffic congestion is a serious problem_ and _

(Round to three decimal places as needed.)

The table to the right shows the results of a survey in which

400 adults from the East,400

adults from the South,400 adults from the Midwest, and 400
adults from the West were asked if traffic congestion is a serious problem. Complete parts (a) and (b).

Adults who say that traffic congestion is a serious problem

EastEast

36%

SouthSouth

33%

MidwestMidwest

25%

WestWest

56%

Explanation / Answer

Confidence Interval For Proportion
CI = p ± Z a/2 Sqrt(p*(1-p)/n)))
x = Mean
n = Sample Size
a = 1 - (Confidence Level/100)
Za/2 = Z-table value
CI = Confidence Interval
Mean(x)=100
Sample Size(n)=400
Sample proportion = x/n =0.25
Confidence Interval = [ 0.25 ±Z a/2 ( Sqrt ( 0.25*0.75) /400)]
= [ 0.25 - 2.58* Sqrt(0) , 0.25 + 2.58* Sqrt(0) ]
= [ 0.194,0.306]

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