The incubation time for a breed of chicks is normally distributed with a mean of 25 days and standard deviation of approximately 2 days. Look at the figure below and answer the following questions. If 1,000 eggs are being incubated, how many chicks do we expect will hatch in the following time periods? (Note: In this problem, let us agree to think of a single day or a succession of days as a continuous interval of time. Assume all eggs eventually hatch.)

Area Under a Normal CurveA graph with a bell-shaped, continuous, and symmetric curve above the horizontal axis is given.
There are 7 equally spaced labels on the axis; from left to right they are: − 3, − 2, − , , + , + 2, and + 3.
The curve enters the viewing window just above the axis at − 3, reaches a peak at , and exits the viewing window just above the axis at + 3.
There are 8 regions under the curve and above the axis labeled with percentage values. Regions with the same percentage value have the same color.
The area under the curve to the left of − 3 is labeled 0.15%.
The area under the curve between − 3 and − 2 is labeled 2.35%.
The area under the curve between − 2 and − is labeled 13.5%.
The area under the curve between − and is labeled 34%.
The area under the curve between and + is labeled 34%.
The area under the curve between + and + 2 is labeled 13.5%.
The area under the curve between + 2 and + 3 is labeled 2.35%.
The area under the curve to the right of + 3 is labeled 0.15%.
68% of the area under the curve lies between − and + .
95% of the area under the curve lies between − 2 and + 2.
99.7% of the area under the curve lies between − 3 and + 3.
(a)
in 21 to 29 days

Incorrect: Your answer is incorrect.
chicks
(b)
in 23 to 27 days

Incorrect: Your answer is incorrect.
chicks
(c)
in 25 days or fewer

Incorrect: Your answer is incorrect.
chicks
(d)
in 19 to 31 days

Incorrect: Your answer is incorrect.
chicks