Aconsumer advocate conducted a test of a popular gasoline additive that was claimed to increase gasoline mileage in cars. for a sample of 15 cars they used the additive and determined how many more miles the car could drive when the additive was added to the gas tank.

for example, a positive 10 would mean that the car drove 10 more miles with the additive whereas a -3 would mean that the car drove 3 fewer miles with the additive.
the table shows a few data values (of how many more miles a car could drive with the additive) along with some summary statistics.

are there any striking deviations?
a) -15
b) -2
c) 7
d) 8
gas additive a
additive values below q1 q1 median q3 values above q3
a -15, -4, -2 1 3 4 5, 7, 8

the things above are just the table.