Download Normal Distribution Practice C

Normal Distribution Practice 5
Name __________________________________________
1) Since the length of a downhill ski is related to the height of the individuals renting them, it is fair to assume that a
normal distribution would describe the length of women’s skis at rental outlets in Queenstown. The mean of the
distribution is 150 cm and the standard deviation is 10 cm.
(a) What is the proportion of women’s ski lengths that are less than 133 cm?
(b) What is the proportion of women’s ski lengths that are greater than 125 cm?
(c) From the 2500 ski rentals during last season, how many would have been for skis that were between 155 and
175cm?
2) Suppose that a certain insect has a mean lifespan of 5.6 days with a standard deviation of 1.2 days.
Assume that the lifespan of this insect is approximately normally distributed.
(a) Calculate the percentage of insects with a life-span between 3 and 8 days.
(b) Calculate the percentage of insects with a life-span between 2 and 3 days.
(c) What percentage of insects will live longer than 6 days?
(d) From a swarm or 500 insects, how many would you expect to live for less than 6.56 days?
Inverse Normal Distribution Practice 6
3) Elephants have the longest pregnancy of all mammals. One species of elephant has a mean gestation period of
525 days and standard deviation of 32 days. Pregnancy length follows an approximately normally distribution.
a) The longest 16% of all elephant pregnancies last at least how many days?
b) The middle 50% of all elephant pregnancies last between ………… and ………… days.
c) Only 5% of all elephant pregnancies last longer than ………… days.
d) The shortest 10% of elephant pregnancies last less than ..........days?
e) The longest 40% of elephant pregnancies last more than ..........days?
f) From a group of 400 pregnant elephants, 50 had ‘early’ births. What is the longest length of pregnancy for an
elephant having an ‘early birth’