Question

There are 300 welders employed at Maine Shipyards Corporation. A sample of 30 welders revealed that 18 graduated from a registered welding course. Construct the 95 percent confidence interval for the proportion of all welders who graduated from a registered welding course. (Round your answers to 3 decimal places!!) The confidence interval is between and

Answer 1

sample success x =		18
sample size          n=		30
sample proportion p̂ =x/n=		0.6000
std error se= √(p*(1-p)/n) =		0.0894
for 95 % CI value of z=		1.960
margin of error E=z*std error   =		0.175
lower bound=p̂ -E                       =		0.425
Upper bound=p̂ +E                     =		0.775

confidence interval is between 0.425 and 0.775