A study looked at the birth weights of 412 babies born in the United States, The
ID: 3225835 • Letter: A
Question
A study looked at the birth weights of 412 babies born in the United States, The mean weight was 3234 grams with a standard deviation of 871 grams. Assume that birth weight data are approximately bell-shaped. Estimate the number of newborns who weighed between 1492 grams and 4976 grams. Write only a number as your answer Round your answer to the nearest whole number. For a population of people who completed their GED, the average age at completion was 29.0 and the standard deviation was 4.0 The distributions of ages was approximately bell-shaped. Compute the z-score for an individual who completed their GED at the age of 20. Write only a number as your answer. (for example: 3.15).Explanation / Answer
first part) here we use stanard normal variate z=(x-mean)/sd
her n=412,mean=3234 and sd=871
for x=1492, z=(1492-3234)/871=-2
for x=4976, z=(4976-3234)/871=2
probability of weighed between 1492 and 4976=p=P(1492<x<4976)
=P(-2<z<2)=P(z<2)-P(z<-2)=0.9772-0.0228=0.9544
requied number=n*p=412*0.9544=393.2128 ( nearest whole number is 393)
answer is 393
second part) here mean=29, sd=4
for x=20, z=(x-mean)/sd=(20-29)/4=-2.25
required z=-2.25
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