The J.O. Supplies Company buys calculators from a foreign supplier. The probability of a defective calculator is 10%.
-If 100 calculators are selected at random,what is the standard deviation of the number of defectives?
A)1.5
B)2.0
C)2.5
D)3.0
E)3.5

Question

Quizplus · Accepted Answer

The standard deviation of a binomial distribution is given by the formula $\sigma = \sqrt{n \cdot p \cdot (1-p)}$, where $n$ is the number of trials (in this case, 100 calculators), and $p$ is the probability of success (in this case, the probability of a calculator being defective, which is 0.10). Plugging in the values, we get $\sigma = \sqrt{100 \cdot 0.10 \cdot (1-0.10)} = \sqrt{100 \cdot 0.10 \cdot 0.90} = \sqrt{9} = 3.0$.

The JO Supplies Company Buys Calculators from a Foreign Supplier