1. ## confidence interval

A 95% confidence interval for a population mean was reported to be 152 to 160. If = 15, what sample size was used in this study?

2. Originally Posted by tonio77
A 95% confidence interval for a population mean was reported to be 152 to 160. If = 15, what sample size was used in this study?
Solve the following equations simultaneously for n:

$\bar{x} - \frac{1.96\sigma}{\sqrt{n}} = 152$ .... (1)

$\bar{x} + \frac{1.96\sigma}{\sqrt{n}} = 160$ .... (1)

where $\sigma = 15$.