Question

6. In a poll of 1000 likely voters, 560 say that the United States spends too little on fighting hunger at home. Find and interpret an 85% confidence interval for the true proportion of voters who feel this way.

Answer 1

sample success x =		560
sample size n=		1000.0
pt estiamte p̂ =x/n=		0.5600
se= √(p*(1-p)/n) =		0.0157
for 85 % CI value of z=		1.440	from excel:normsinv((1+0.85)/2)

margin of error E=z*std error   =		0.023
lower bound=p̂ -E                       =		0.5374
Upper bound=p̂ +E                     =		0.5826
from above 85% confidence interval for population proportion =(0.5374 ,0.5826)

above interval gives 85% confidence to contain true value of population proportion of voters who feel this way