Question

Bags of chips are filled using a machine. Because not all chips are the same size, it is impossible to get the exact target weight in each bag. The target weight is 75 g. Based on samples of size 4, the average standard deviation is about 0.5 g,and the average weight of the last batch of four bags was 76 g. Which of the following are the upper and lower control limits for an x control chart?

A) (73.5, 76.5) g

B) (74.25, 75.75) g   

C) (74.5, 77.5) g

D) (76.25, 76.75) g

Answer 1

We have n =4 , targeted mean = = 75 , from sample we get mean = = 76, average standard deviation = = 0.5

The control limits are :

A₃ can be determined using tables of constant for control chart. Look in to row of n =4 and find value of A₃ .

= 75.19

  

= 76.81