Let a represent the battery life of a brand A laptop, and let b represent the battery life of a brand B laptop. The mean difference in battery life between these two brands of laptops, d = a - b, is -3.25 hours. What is the correct interpretation of this value?
a) Brand A has 3.25 hours more battery life than Brand B on average.
b) Brand B has 3.25 hours more battery life than Brand A on average.
c) The brands have equal battery life on average.
