Question 612405
a researcher is interested in estimating the noise levels in decibels at area urban hospitals. she wants to be 95% confident that her estimate is correct. If the standard deviation is 5.48, how large a sample is needed to get the desired information to be accurate within 0.68 decibels. 
---------
Since E = z*s/sqrt(n)
---
n = [z*s/E]^2
n = [1.96*5.48/0.68]^2 = 250 when rounded up
===================
Cheers,
Stan H.