A headphone manufacturer wants to ensure that their headphones achieve their rated impedance of 96chms, because they want to test compliance as efficiently as possible. A prior study for the same type of manufactured headphones gives the standard deviation as 4chms. Find the minimum sample size to have a margin of error less than one and a 95% confidence interval.

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters