Fewer young people are driving. in 1983, 87% of 19-year-olds had a driver’s license. twenty-five years later that percentage had dropped to 75% (university of michigan transportation research institute website, april 7, 2012). suppose these results are based on a random sample of 1200 19-year-olds in 1983 and again in 2008. a. at 95% confidence, what is the margin of error and the interval estimate of the number of 19-year-old drivers in 1983? b. at 95% confidence, what is the margin of error and the interval estimate of the number of 19-year-old drivers in 2008? c. is the margin of error the same in parts (a) and (b)? why or why not?

Formula to find the margin of error :

, where n= sample size  , is the sample proportion and z*= critical z-value.

Let p be the proportion of 19-year-olds had a driver’s license.

A) As per given , In 1983

n=  1200

Critical value for 95% confidence level is 1.96 (By z-table)

So ,Margin of error :

Interval :

B) In 2008 ,

Margin of error :    

Interval :

c. The margin of error is not the same in parts (a) and (b) because the sample proportion of 19-year-olds had a driver’s license are not same in both parts.

2nd one in the first row is correct

answer:   x = 3 + √11     and     x = 3 - √11

step-by-step explanation:

x² - 6x + 9 = 11

(x - 3)² = 11

x - 3 = ±√11

    x = 3 ± √11

x = 3 + √11     and     x = 3 - √11