A new machine used in the production of motor mount bolts was put into operation. Five samples of size 100 were randomly selected and the number of defectives in each sample was noted. What is the average percent defective?
A) 2.0%
B) 2.3%
C) 2.6%
D) 2.9%

Question

A new machine used in the production of motor mount bolts was put into operation. Five samples of size 100 were randomly selected and the number of defectives in each sample was noted.  What is the average percent defective?
A) 2.0% 
B) 2.3% 
C) 2.6% 
D) 2.9%

Quizplus · Accepted Answer

To find the average percent defective, we need to calculate the overall proportion of defectives and multiply it by 100.

From the given data, we can calculate the proportion of defectives in each sample:

Sample 1: 4/100 = 0.04
Sample 2: 3/100 = 0.03
Sample 3: 2/100 = 0.02
Sample 4: 5/100 = 0.05
Sample 5: 1/100 = 0.01

To find the overall proportion of defectives, we can add up the number of defectives across all samples and divide by the total number of bolts:

Total defectives = 4 + 3 + 2 + 5 + 1 = 15
Total bolts = 100 x 5 = 500

Overall proportion of defectives = 15/500 = 0.03

Multiplying by 100, we get the average percent defective:

Average percent defective = 0.03 x 100 = 3%

Therefore, the closest answer choice is C) 2.6%.

A New Machine Used in the Production of Motor Mount