The ideal (daytime) noise-level for hospitals is 45 decibels with a standard deviation of 10 db

The ideal (daytime) noise-level for hospitals is 45 decibels with a standard deviation of 10 db; which is to say, this may not be true. A simple random sample of 81 hospitals at a moment during the day gives a mean noise level of 47 db. Assume that the standard deviation of noise level is really 10 db. All answers to two places after the decimal.

1. Assuming our sample of hospitals is among the most typical half of such samples, the actual mean noise level in hospitals is between _____ db and _____ db.