268 CHAPTER 6 The Normal Distribution and Other Continuous
6.5 Given a normal distribution with = 70 and o = 20, what
is the probability that
a. X > 110.
b. X < 10.
c. X< 70 or X > 130.
d. Between what two X values (symmetrically distributed around
the mean) are 70% of the values.
8
6.6 Given a normal distribution with μ = 30 and σ = 4, what is
the probability that
a. X > 38.
b. X < 25.
c. Find the X value such that the area to the left of X is 5% of the
total area under the normal curve.
d. Between what two X values (symmetrically distributed around
the mean) are 40% of the values?
P(Z > 2) = (1-0,9094 = 00228
P(25-1.2²) 011056
27:25-30
4
1125
5x1165
Z=30+4
1-905=0.95
(₁28-1
46.64 = 3