Question

Suppose babies born after a gestation period of 32 to 35 weeks have a mean weight of 29002900 grams and a standard deviation of 800800 grams while babies born after a gestation period of 40 weeks have a mean weight of 32003200 grams and a standard deviation of 500500 grams. If a 3232​-week gestation period baby weighs 24002400 grams and a 4040​-week gestation period baby weighs 27002700 ​grams, find the corresponding​ z-scores. Which baby weighs lessless relative to the gestation​ period?
The 3232​-week gestation period baby weighs
nothing standard deviations
▼
above
below
the mean.
The 4040​-week gestation period baby weighs
nothing standard deviations
▼
above
below
the mean.
​(Round to two decimal places as​ needed.)

Answer 1

$x_{32}=2400\implies z_{32}=\dfrac{2400-2900}{800}=-0.625\approx-0.63$

$x_{40}=2700\implies z_{40}=\dfrac{2700-3200}{500}=-1$

So the 32g baby weighs about 0.63 standard deviations *below* the mean, while the 40g baby weighs 1 standard deviation *below* the mean.