Suppose that the mean birthweight for newborn babies in USA is 150 oz and the st

Question

Suppose that the mean birthweight for newborn babies in USA is 150 oz and the standard deviation () is 24 oz. Paul suspects that the mean birthweight (u) of the low-SES newborn babies in USA might be lower than that of all newborn babies in USA. Assume the distribution of birthweights is normal.

a) What test will you use to perform the hypothesis test?

b. at a significance level of 5%, what's the statistical power given n=100 and the true average birthweight for low-SES newborn babies in USA is 145? which option is correct:

a) 5%

b) 33%

C) 45%

d) 67%

Explanation / Answer

H1: µ < 150

The level of significance is 5% so the critical value we get from Normal Table as -1.645

z = ( x bar - µ ) / ( s / Ön)

Reject H0 if,

z -1.645    

             (x bar – 150)/(24/Ö100) -1.645

             x bar = 146.052

            Power of the test = ( x bar 146.052)

            z = ( x bar - µ) / ( s/ Ön )

z1 = (146.052– 145)/(24/Ö100) = 0.44

P ( z 0.44 )

By using Normal Distribution table we get,

                P (z0.44) = 0.6700 ~ 67%

        Answer:

d) 67%

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