To solve this problem, we use the formula:
z = (x – u) / s
where z is the z score value which can be obtained from
the tables, x is the sample value, u is the mean = 6.3 min, and s is the std
dev = 2.2 min
at P value = 0.90, the z = 1.28, finding for x:
x = z s + u
x = 1.28 * 2.2 + 6.3
x = 9.116
at P value = 1.0, the z = 3.49, finding for x:
x = z s + u
x = 3.49 * 2.2 + 6.3
x = 13.978 ~ 14
Therefore the longest 10% calls last about 9.1 minutes to
14 minutes
The origin is (0,0)
y = mx + b
slope(m) = 2/3
(0,0)...x = 0 and y = 0
now we sub and find b, the y int
0 = 2/3(0) + b
0 = b
so ur equation is y = 2/3x + 0...or just y = 2/3x
