WA107 PLEASE SHOW ALL WORK Consumers turned to their mobile

WA10_7 PLEASE SHOW ALL WORK

Consumers turned to their mobile devices in growing numbers and increasing frequency throughout a given year. Text messaging led as the top mobile activity, with 63% of American mobile subscribers texting that year. A polling firm contacts an SRS of 1100 people chosen from the population of American mobile subscribers. Give the 95% confidence interval for the true proportion of mobile users who text? (Round your answers to three decimal places.)

Solution

n =1000

p = 63% =0.63
1-p = 0.37

p(1-p)/n = Variance = 0.000111

Std error = 0.01053

Margin of error for 95% = 1.96*std error = 0.0196

Hence confidence interval lower bound = 0.63-0.0196= 0.6104

Upper bound = 0.63+0.0196 =0.6496