Question

After graduation, you accept a position as Purchasing Manager for Dockery Manufacturing (how exciting!). You are qualifying a source for leverage items and require a lead time between 18 and 23 days. After examining the supplier’s bid information, you determine their current lead times are normally distributed and have a process mean of 21 days. If the target capability is 1.33, then what maximum standard deviation can the process have to be considered capable?
a. 0.50
b. 0.63
c. 0.67
d. 0.75
e. 1.00

Answer 1

Answer:

b. 0.63

Explanation:

Given that:

The Purchasing Manager for Dockery Manufacturing is qualifying a source for leverage items and require a lead time between 18 and 23 days.

We can say that the Lower specification limit LSL = 18 and Higher specification limit USL = 23

Mean = 21

The target capability is 1.33

The objective is to determine the maximum standard deviation can the process have to be considered capable

From above ;

The process capability can be determined by the formula:

$Process Capability = \dfrac{(USL -LSL)}{(6*standard \ deviation)}$

$Process \ Capability = \dfrac{(23 -18)}{(6*standard \ deviation)}$

The process capability requires  to be minimum (1.33) in order to be capable;

Thus;

$1.33 = \dfrac{(23 -18)}{(6*standard \ deviation)}$

$1.33 = \dfrac{(5)}{(6*standard \ deviation)}$

standard deviation = $\dfrac{(5)}{(6*1.33)}$

standard deviation = 0.6265

standard deviation = 0.63