Babies weighing 5.5 pounds or less at birth are said to have low birth weights, which can be dangerous. Full-term birth weights for single babies (not twins or triplets or other multiple births) are normally distributed with a mean of 7.5 pounds and a standard deviation of 1.1 pounds.
a. For one randomly selected full-term single-birth baby, what is the probability that the birth weight is 5.5 pounds or less?
b. For two randomly selected full-term, single-birth babies, what is the probability that both have birth weights of 5.5 pounds or less?
c. For 200 random full-term single births, what is the approximate probability that 7 or fewer have low birth weights?
d. If 200 independent full-term single-birth babies are born at a hospital, how many would you expect to have birth weights of 5.5 pounds or less? Round to the nearest whole number.
e. What is the standard deviation for the number of babies out of 200 who weigh 5.5 pounds or less? Retain two decimal digits for use in part f.
f. Report the birth weight for full-term single babies (with 200 births) for two standard deviations below the mean and for two standard deviations above the mean. Round both numbers to the nearest whole number.
g. If there were 45 low-birth-weight full-term babies out of 200, would you be surprised?

  • CreatedJuly 16, 2015
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