4.9. For a normally distributed variable, verify that the probability between:

(a) and + equals 0.68

(b) - 1.960 and 1.960 equals 0.95

(c)

(d) 30 and + 30 equals 0.997 0.670 and +0.67o equals 0.50 4.10. Find the z-value for which the probability that a normal variable exceeds +zo equals

(a) 0.01

(b) 0.025

(e) 0.05

(d) 0.10

(e) 0.25 (0) 0.50?