# Math Help - One more question

1. ## One more question

10% of items produced by a machine are defective. Out of 15 items chosen at random,

a. what is the probability that exactly 3 items are defective?

b. probability less than 3 items are defective?

c. probability that exactly 11 items will be non-defective?

THANK YOU

2. Originally Posted by hpquintero
10% of items produced by a machine are defective. Out of 15 items chosen at random,

a. What is the probability that exactly 3 items are defective?
$0.1^{3} * 0.9^{12}$

b. Probability less than 3 items are defective?
$0.1^{2} * 0.9^{13}+0.1 * 0.9^{14}+0.9^{15}$

c. Probability that exactly 11 items will be non-defective?

$0.1^{11} * 0.9^{4}$

3. Originally Posted by RhysGM
$0.1^{3} * 0.9^{12}$

$0.1^{2} * 0.9^{13}+0.1 * 0.9^{14}+0.9^{15}$

$0.1^{11} * 0.9^{4}$
Sorry but all these answers are wrong.

Let X be the random variable number of defective items.

X ~ Binomial(n = 15, p = 0.1)

(a) Calculate $\Pr(X = 3)$.

(b) Calculate $\Pr(X \leq 2)$.

(c) Calculate $\Pr(X = 4)$.