In a simple random sample of 1200 Americans age 20 and over, the proportion with diabetes was found to be $0.115$ (or $11.5 \%)$.
a. What is the standard error for the estimate of the proportion of all
Americans age 20 and over with diabetes?
b. Find the margin of error, using a $95 \%$ confidence level, for estimating this proportion.
c. Report the $95 \%$ confidence interval for the proportion of all Americans
age 20 and over with diabetes.
d. According to the Centers for Disease Control and Prevention, nationally, $10.7 \%$ of all Americans age 20 or over have diabetes. Does the confidence interval you found in part c support or refute this claim? Explain.