In: Statistics and Probability
A random sample of 1900 workers in a particular city found 399 workers who had full health insurance coverage. Find a 95% confidence interval for the true percent of workers in this city who have full health insurance coverage. Express your results to the nearest hundredth of a percent.
Answer: to %
sample size = n = 1900
x = 399
p = x/n = 0.21
zα = 1.96 at 95% confidence
standard error = s.e. = √[p(1-p)/n] = 0.00934429181
margin of error = E = s.e.× zα = 0.00934429181 × 1.96 = 0.0183148119
95% confidence interval for this proportion ( p – E; p + E ) = ( 0.1916851880 ,0.2283148119 )
= (0.19; 0.23) [Approx.]