- A forest products company claims that the amount of
usable lumber in its harvested trees averages 172 cubic
feet and has a standard deviation of 12.4 cubic feet.
Assume that these amounts have approximately a normal
distribution.
- What proportion of trees contain more than 150 cubic feet?
- What proportion of trees contain between 175 and 190 cubic feet?

- At two years of age, sardines inhabiting Japanese waters
have a length distribution that is approximately normal
with mean 20.20 cm and standard deviation 0.65 cm.
- What proportion of these sardines are between 19.0 and 21.0 cm long?
- How long are the longest 15% of all these sardines?
- How short are the shortest 15% of all these sardines?
- In what range do the middle 70% of all sardines fall?

- The mean cholesterol level in children is 175 mg/dL with
standard deviation 35 mg/dL. Assume this level varies
from child to child according to an approximate normal
distribution.
- What percentage of children have a cholesterol level above 200 mg/dL?
- How high are the levels for the highest 2% of all children?

- Porphyrin is a pigment in blood protoplasm and other body
fluids that is significant in body energy and storage. In
healthy Alaskan brown bears, the amount of porphyrin in
the bloodstream (in mg/dL) has approximate normal
distribution with mean 47.5 and standard deviation 12.2.
- What proportion of these bears have between 27.5 and 67.5 mg/dL porphyrin in their bloodstream? (That’s within 20 of the mean amount of 47.5.)
- How low are the porphyrin levels for the lowest 3% of all the bears?

- Healthy 10-week-old domesticated kittens have average
weight 24.5 oz. with a standard deviation of 5.25 oz. The
distribution is approximately normal.
- A kitten is designated as dangerously underweight when, at 10 weeks, it weighs less than 10.0 oz. What proportion of healthy kittens will designated as dangerously underweight?
- What is the median weight of the kittens?
- What are the first and third quartiles of the
kitten weights? (25% of the kittens weigh less
than Q
_{1}; 75% weigh more. 75% of the kittens weigh less than Q_{3}; 25% weigh more.) What is the interquartile range (IQR) for the kitten weights?

- a) 0.9616; b) 0.3317
- a) 0.8585; b) above 20.88 cm; c) below 12.52 cm; d) between 19.52 and 20.88 cm
- a) 23.89%; b) above 246.75 mg/dL
- a) 0.8990; b) below 24.564 mg/dL
- a) 0.0029; b) 24.5 oz; c) Q
_{1}= 20.98 oz, Q_{3}= 28.02 oz, IQR = 7.04 oz.