Question

A CI is desired for the true average stray-load loss μ (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 σ = 3.16.
(Round your answers to two decimal places. You must enter the LOWER BOUND first then the UPPER BOUND second.)

(a) Compute a 95% CI for μ when n = 25 and x = 59.40

( , ) watts

(b) Compute a 95% CI for μ when n = 100 and x = 59.40.

( , ) watts

(c) Compute a 99% CI for μ when n = 100 and x = 59.40.

( , ) watts

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

Answer 1

a)

95% CI for μ =58.16 ;60.64

b)

as above 95% CI for μ =58.78 ; 60.02

c)

99% CI for μ =58.58 ; 60.22 ( please try 58.59 ; 60.21 if this comes wrong)

d)

for 99 % CI value of z=	2.576
standard deviation σ=	3.16
margin of error E =	0.5
required sample size n=(zσ/E)2                                         =	266.0