Statistics Problem

faolain

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Nov 8, 2013
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I registered on this forum just to ask this question I am having trouble with. Here it is:

The mean weight of babies born to full term pregnancies is 7lbs with a standard deviation of 14 oz


A woman has an ultrasound two weeks before the baby is due and the doctor determines the baby is already 7lbs. What is the probability that when the baby is born it will weight more than 7.5lbs?


7lbs = 112 oz
7.5lbs = 120oz

I am not really sure how to begin.
I've got the z-score for 120oz using (120-112)/14 = 0.57142
Then I used a Z-score chart to get 0.7157.

What I don't understand is how to take into account that the baby is not at full term yet. Any help would be much appreciated.

 
I registered on this forum just to ask this question I am having trouble with. Here it is:

The mean weight of babies born to full term pregnancies is 7lbs with a standard deviation of 14 oz


A woman has an ultrasound two weeks before the baby is due and the doctor determines the baby is already 7lbs. What is the probability that when the baby is born it will weight more than 7.5lbs?


7lbs = 112 oz
7.5lbs = 120oz

I am not really sure how to begin.
I've got the z-score for 120oz using (120-112)/14 = 0.57142
Then I used a Z-score chart to get 0.7157.

What I don't understand is how to take into account that the baby is not at full term yet. Any help would be much appreciated.

If you draw the normal distribution, it will have a lower part that extends to weights less than the already achieved weight of 7 pounds. That part of the distribution must be discarded. What fraction of the normal curve is then possible? In this case, exactly half .. only the half above the mean of the distribution. Find the area above z=0.7157, and normalize that to the "possible" area of 0.500 [that is, multiply by 2].
 
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