A CI is desired for the true average strayload loss watts f

A CI is desired for the true average stray-load loss ? (watts) for a certain type of induction motor when the line current is held at 10 amps for a speed of 1500 rpm. Assume that stray-load loss is normally distributed with ? = 2.9. (Round your answers to two decimal places.)

How large must n be if the width of the 99% interval for ? is to be 1.0? (Round your answer up to the nearest whole number.)

Solution

Given a=1-0.99=0.01, Z(0.005) = 2.58 (from standard normal table)

E=1/2=0.5

So n=(Z*s/E)^2

=(2.58*2.9/0.5)^2

=223.9213

Take n=224