The ideal (daytime) noise-level for hospitals is 45 decibels with a standard deviation of 11 db; which is to say, this may not be true . A simple random sample of 80 hospitals at a moment during the...

Theideal (daytime) noise-level for hospitals is 45 decibels with a standard deviation of 11 db; which is to say,this may not be true. A simple random sample of 80 hospitals at a moment during the day gives a mean noise level of 47 db. Assume that the standard deviation of noise level for all hospitals is really 11 db. All answers to two places after the decimal.
(a) A 99% confidence interval for the actual mean noise level in hospitals is (  db,   db).
(b) We can be 90% confident that the actual mean noise level in hospitals is  db with a margin of error of   db.
(c) Unless our sample (of 80 hospitals) is among the most unusual 2% of samples, the actual mean noise level in hospitals is between   db and   db.