confidence interval

#1
I have a problem I would like to know if I am doing it right.

Use the degree of confidence and sample data to construct a confidence interval for the population mean. Assume that the population has a normal distribution.

A laboratory tested 12 chicken eggs and found the mean amount of cholesterol was 230 milligrams with s= 13.8 milligrams. Construct a 95 percent confidence interval for the true mean cholesterol content of all such eggs.

(my work)
N=12, x=.05, x/2=.025, DF=11, SD=13.8, 95% conf, (mean amount) x=230

E= T(11, .025) x S/(square root) N
2.201 x 13.8 / (square root) 12 = 8.768 (should I round this to 9?)

230 - 8 < m < 230 + 8 =
222 < m < 238
 

JohnM

TS Contributor
#2
Your logic and computation is correct, just don't round anything until you've gotten your final answer.

You should get 230 +/- 8.76