A manufacturer of iPhone batteries has established that the median time it takes for a battery to lose its charge is 11 hours. A sample of 40 iPhone batteries from a competitor is obtained, and the batteries are tested continuously until each fails to hold a charge. Of the 40 failure 25 exceeded 11 hours, 14 were less than 11 hours, and 1 was 11 hours. Is there evidence that the median failure time of the competitor's batteries differ from 11 hours? Use large sample test with = 1%.

I changed the numbers in the above problem so I can learn to do it by hand. I am having trouble finding the formulas and don't really know how to show the work. If somebody can break it down for me showing the work it'd be great so I can turn in my HW. Please and Thank You!