Biology Forums - Study Force

A pizza delivery service wants to track their delivery times. They take eight samples of four deliveries and record the following data. What are the upper and lower control limits of their X-bar chart?
 
  Sample  1 2 3 4 5 6 7 8
  Item 1 21.1 20.2 24.1 22.6 21.2 20.9 22.4 20.9
  Item 2 21.7 20.6 21.7 21.7 24.1 23.5 24.6 24.7
  Item 3 23.0 24.5 23.2 23.0 20.6 22.8 23.4 22.8
  Item 4 20.3 23.5 24.4 25.0 20.7 23.2 23.3 24.5
  Sum 86.1 88.8 93.4 92.3 86.6 90.4 93.7 92.9
 
  A) 24.9, 20.3
  B) 23.8, 21.4
  C) 22.6, 19.5
  D) 21.1, 17.6

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