Plastic strips that are used in a sensitive electronic device are manufactured t
ID: 3225412 • Letter: P
Question
Plastic strips that are used in a sensitive electronic device are manufactured to a maximum specification of 305.70 mm (approximately 12.04 in) and a minimum specification of 304.55 mm (approximately 11.99 in). If the strips are less than the minimum specification, they are scrapped; if they are greater than the maximum specification, they are reworked. The part dimensions are normally distributed with a population mean of 305.20 mm (approximately 12.02 in) and a standard deviation of 0.25 mm. What is the expected percentage of scrap and What's the expected percentage of rework? SHOW CALCULATIONS
a. 0.10% scrap; 6.43% rework
b. 2.27% scrap; 0.47% rework
c. 47% scrap; 2.27 % rework
d. 6.43% scrap; 0.10% rework
Explanation / Answer
Let X denote part dimenstion then X follows normal distribution
Expected Percentage of scrap)=100*P(X<304.55) = 100*0.0047 =0.47% using excel fucntion =NORMDIST(304.55,305.2,0.25,TRUE)
Expected Percentage of rework=100*[1-P(X>305.70)] = 100*0.0228 =2.28%
using excel fucntion =1-NORMDIST(305.70,305.2,0.25,TRUE)