A company sells light bulbs in packages of 20 and estimates that the mean number of defective light bulbs in a package is 0.6 with a standard deviation of 0.7.If a customer buys 12 packages,what are the expected value and standard deviation of the number of defective light bulbs? Assume that packages are independent of each other.
A)μ = 7.2,σ = 2.42
B)μ = 7.2,σ = 100.8
C)μ = 2.08,σ = 8.4
D)μ = 7.2,σ = 8.4
E)μ = 2.08,σ = 2.42

Question

Quizplus · Accepted Answer

The expected value (mean) of defective light bulbs in 12 packages is 12 * 0.6 = 7.2. The standard deviation for 12 packages is sqrt(12) * 0.7 ≈ 2.42, since standard deviation scales with the square root of the number of packages.

A Company Sells Light Bulbs in Packages of 20 and Estimates