The Quality Control Manager of a Major Cell Phone Provider

Multiple Choice

The quality control manager of a major cell phone provider is concerned about the life of the cell phone batteries they use.He took a sample of 13 batteries from a recent shipment and used them continuously until they failed to work.The manager measured the number of hours the batteries lasted and found the mean to be 550.4 with a standard deviation of 315.3.Calculate the appropriate test statistic to test the claim that the mean life of the batteries is more than 400 hours.

A) 6.20
B) 1.72
C) 0.477
D) -6.20
E) -1.72