I been having trouble finding confidence level.
Example: A Sample of 16 days has a sample mean of 48 rooms. This information is used to calculate an interval estimate for the population mean to be from 40 to 56 rooms.

What is the level of confidence of this interval?

I have no idea how to approach question like that.

You need the standard deviation to do that. Your numbers are 8 off the mean, but you have to divide that by the standard deviation to know how many s.d.'s that is. From there you should have some type of chart to look it up on. Whether you need a z or a t chart will depend on how your text does certain things.