In a factor producing light bulb, any light bulb that does not light up within 3 seconds will be taken as a defect and should be rejected. The factory manager felt that the number of defects has been rising recently but he is not sure whether this should be brought up to the attention of the management. He collected random samples from the production line over the last 15 hours and the data is presented in a check sheet as below. Is the process in control according to a 2-sigma control limits? Why?

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