Question: A medical facility does MRIs for sports injuries. Occasionally a test yields inconclusive results and must be repeated. Using the following sample data and n=200, determine the upper and lower control limits for the fraction of retests using two-sigma limits. Is the process in control?

Sample

1 2 3 4 5 6 7 8 9 10 11 12 13

# of results

1 2 2 0 2 1 2 0 2 7 3 2 1