
Chapter 6
232
(b) Probability of nding eight or fewer defectives in a batch
P(x ≤ 8/l = 10)
= P(x = 0) + P(x = 1) + P(x = 2) + P(x = 3) + P(x = 4) + P(x = 5) + P(x = 6) + P(x = 7)
+ P(x = 8) = 0.000045 + 0.000454 + 0.002270 +0.007567 + 0.018917 + 0.037833
+ 0.063055 + 0.090079 + 0.112599
= 0.3328
(c) Probability that the batch contains 6 < x < 10 defectives
P(6 < x < 10/l = 10)
= P(x = 7) + P(x = 8) + P(x = 9) = 0.090079 + 0.112599 + 0.125110 = 0.3277
(d) Probability that the batch contains 6 ≤ x ≤ 10 defectives
P(6 ≤ x ≤ 10 / l = 10)
= P(x = 6) + P(x = 7) + P(x = 8) + P(x = 9) + P(x = 10)
= 0.063055 + 0.090079 + 0.112599 + 0.125110 ...