Given an average of 1.84 defects per 5 units, what is the upper limit of the control chart to be set?

OPTIONS

• 2.944
• 3.66
• 3.287
• 5

ANSWER

3.66

EXPLANATION

This is a case of u-chart (count defects and sub-group size may not be constant) u-bar = 1.84 n = 5 UCL = u-bar + 3 * SQRT (u-bar/n) UCL = 1.84 + 3 * SQRT (1.84/5) UCL = 1.84 + 3 * 0.60663 UCL = 3.66