(a) Supposexhas a normal distribution with=6. A random sample of size11has a sample mean ofx= 50.

Find a 90% confidence interval for mu. What is the margin of error? (Round your answers to two decimal places.)

• lower limit=
• upper limit=
• margin of error =

(b) Supposexhas a normal distribution with=14. A random sample of size43has a sample mean ofx= 70.

Find a 95% confidence interval for mu. What is the margin of error? (Round your answers to two decimal places.)

• lower limit=
• upper limit=
• margin of error =

(c) Supposexhas a normal distribution with=3. Find the minimal sample size required so that for a 95% confidence interval, the maximal margin of error isE=0.1

• minimum sample size=

(d) Supposexhas a normal distribution with=1.3. Find the minimal sample size required so that for a 90% confidence interval, the maximal margin of error isE=0.9

• minimum sample size=