Question

Plastic parts produced by an injection-molding operation are checked for conformance to specifications. Each tool contains 10 cavities in which parts are produced, and these parts fall into a conveyor when the press opens. An inspector chooses 2 part(s) from among the 10 at random. Two cavities are affected by a temperature malfunction that results in parts that do not conform to specifications.

a. How many samples contain exactly 1 nonconforming part?
b. How many samples contain at least 1 nonconforming part?

Answer 1

16 ;

17

Explanation:

Number of cavities = 10

Number of parts chosen = 2

Number of cavities affected by temperature malfunction = 2

A.)

Number of samples that contain exactly one conforming part :

2C1 * 10-2C2-1

2C1 * 8C1

Combination formula :

nCr = n! ÷ (n-r)! r!

Using calculator :

2C1 * 8C1 = 2 * 8 = 16

B)

b. How many samples contain at least 1 nonconforming part?

10C2 - 8C2 = 45 - 28 = 17