Assuming that weights of newborn babies at a certain hospita

Assuming that weights of newborn babies at a certain hospital are normally distributed with mean 6.5 pounds and standard deviation 1.2 pounds, how many babies in a group of 80 babies from this hospital will weigh more than 8.9 pounds?

Solution

The probability that weigh is more than 8.9 pounds is

P(X>8.9) = P((X-mean)/s >(8.9-6.5)/1.2)

=P(Z>2) = 0.0228 (from standard normal table)

SO 80*0.0228=1.824

Answer: 2 babies