There were 1 , 4 3 4 complaints from the 1 , 3 8 , 6 0 0 patients treated between Mar. 2 0 1 1 and Dec. 2 0 1 2 . At what sigma level is the overall hospitality service at the hospital operating? ( Hint: Assume each complaint as a defective and 1 , 4 3 4 unhappy patients. Calculate percent defectives. Get % non - defectives as process yield or meeting expectations. Now find Z - score corresponding to the process yield using Z - table as the sigma level )