Question

The incubation time for Rhode Island Red chicks is normally distributed with mean of 30 days and standard deviation of approximately 2 days. If 1000 eggs are being incubated, how many chicks do we expect will hatch in 26 to 36 days?

a)136

b)840

c)819

d)976

e)499

Answer 1

Given,

= 30 , = 2

We convert this to standard normal as

P( X < x) = P (Z < x - / )

So,

P( 26 < X < 36) = P (X < 36) - P(X < 26)

= P( Z < 36 - 30 / 2) - P( Z < 26 - 30 / 2)

= P( Z < 3) - P( Z < -2)

= 0.9987 - 0.0228

= 0.9759

Of the 1000 eggs we expect , 1000 * 0.9759 = 975.9

976