When a virus is placed on a tobacco leaf, small lesions appear on the leaf. To compare the number of lesions produced by two different strains of a virus, one strain is applied to half of each of 8 tobacco leaves, and the other strain is applied to the other half of each leaf. The strain that goes on the right half of each leaf is decided with a coin flip. The data are given below. What is the number of degrees of freedom associated with the appropriate t test for testing to see if there is a difference between the mean number of lesions per leaf produced by the two strains? 11 7 11.53 8 12.01