Question

An assembly consists of two mechanical components. Suppose that the probabilities that the first and second components meet specifications are 0.89 and 0.84. Assume that the components are independent. Determine the probability mass function of the number of components in the assembly that meet specifications. X = number of components that meet specifications. Round your answers to four decimal places (e.g. 98.7654).

Answer 1

P(X = 0) = 0.0176

P(X = 1) = 0.2348

P(X = 2) = 0.7476

Explanation:

Because there are 2 mechanical components you have 3 differents scenarios:

1. The 2 components dont meet the specification (X = 0)

2. 1 of the 2 component doesnt meet the specification (X = 1)

3. The 2 components meet the specification. (X = 2)

P(A) = 0.89

The probability that A doesnt meet the specification is 1- P(A) = 0.11

P(B) = 0.84

The probability that A doesnt meet the specification is 1- P(B) = 0.16

Then using those probabilities to determine the probabilities of each scenario you get:

1. The 2 components dont meet the specification

P (X = 0) = (1 - P(A)) * (1- P(B))

P (X = 0) = 0.11 * 0.16 = 0.0176

2. 1 of the 2 component doesnt meet the specification (X = 1)

P (X = 1) = P(A)*(1- P(B)) + P(B)*(1 - P(A)) /// (The probability that A meets specification and B doesnt or B that meets specification and A doesnt)

P (X = 1) = 0.89*0.16 + 0.84*0.11 = 0.2348

3. The 2 components meet the specification. (X = 2)

P(X = 2) = 0.89*0.84 = 0.7476