Two machines make the same product and the dimension of interest is 1.500 ± 0.03
ID: 2073346 • Letter: T
Question
Two machines make the same product and the dimension of interest is 1.500 ± 0.03 inches. Based on the measurements done for the control chart, parts made on machine A had diameter 1.508 (mean) inches and the standard deviation 0.017 in, while the average diameter made on machine B is 1.512 with standard deviation 0.012in. Select a statement or statements that hold in this situation (there can be more than 1 choice):
Machine A is more accurate
Machine A is more precise
Machine B is more precise
Machine B is more accurate
Both machines have the same precision and accuracy
a.Machine A is more accurate
b.Machine A is more precise
c.Machine B is more precise
d.Machine B is more accurate
e.Both machines have the same precision and accuracy
Explanation / Answer
Options= a and b.
Accuracy refers to the closeness of a measured value to a standard or known value.
Precision refers to the closeness of two or more measurements to each other.
As we can see that in case of machine A the mean diameter is 1.508 inches, which is close to the mean known value 1.5 inches. But it has got large standard deviation compared to machine B. The larger the standard deviation, the lower the quality of the manufacturing process. So machine A is only accurate, but not precise. Whereas machine B produces components with mean dia 1.512 which is greater than the mean dia of machine A. So machine B is not as accurate as machine A. But if we look at standard deviation value, machine B standard deviation value is less than that of machine A, which means within the manufacturing process with machine B, there is less variation and hence machine B is more precise compared to machine A.
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