If = 23 ounces, σ = 0.4 ounces, and n = 16, what will be the ±3σ control limits for the x-bar chart?

a) 21.8 to 24.2 ounces
b) 23 ounces
c) 22.70 to 23.30 ounces
d) 22.25 to 23.75 ounces
e) 22.90 to 23.10 ounces

C) 22.70 to 23.30 ounces

Explanation:

Process average = 23

σ = 0.4 ounces

σx = σ/sqrt(n)

where n = sample size

σx = 0.4/sqrt(16)

     = 0.4/4

      = 0.1

UCL= Process average + zσx   LCL = Process average - zσx

UCL= 23 + 3*0.1

       = 23.3

LCL= 23 - 3*0.1

      = 22.7

Therefore, The control limits will be 22.7 for the ±3σ control limits for the x-bar chart.

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