A Quality Analyst wants to construct a control chart for determining whether three machines,all producing the same product,are under control with regard to a particular quality variable.Accordingly,he sampled four units of output from each machine,with the following results: What is the sample average range based upon this limited sample?
A)2.0
B)4.33
C)5.4
D)6.0
E)9.0

Question

A Quality Analyst wants to construct a control chart for determining whether three machines,all producing the same product,are under control with regard to a particular quality variable.Accordingly,he sampled four units of output from each machine,with the following results:  What is the sample average range based upon this limited sample?
A)2.0 
B)4.33 
C)5.4 
D)6.0 
E)9.0

Quizplus · Accepted Answer

To calculate the sample average range, we need to find the range of each sample (the difference between the highest and lowest values). Then, we can find the average of those ranges.

Machine 1: Range = 12-8 = 4
Machine 2: Range = 11-5 = 6
Machine 3: Range = 9-5 = 4
Machine 4: Range = 10-7 = 3

Average range = (4+6+4+3)/4 = 4.25
The closest option to that average is B) 4.33.

A Quality Analyst Wants to Construct a Control Chart for Determining