In 2002, the median pH level of the rain in Glacier National Park, Montana, was 5.25. A biologist thinks that the acidity of rain has decreased since then, which would suggest the pH has increased. She obtains a random sample of 15 rain dates in 2015 and obtains the following data:

Test the hypothesis that the median pH level has increased from 5.25 at the α = 0.05 level of significance.