The manufacturer of a gasoline additive claims that the use of this additive increases’ gasoline mileage. A random sample of 6 cars was selected, and these cars were driven for one week without the...

The manufacturer of a gasoline additive claims that the use of this additive increases’
gasoline mileage. A random sample of 6 cars was selected, and these cars were driven
for one week without the gasoline additive and then for one week with the additive.
The following table gives the mileage (in miles per gallon) for these cars with and
without the additive:

Assuming mileage are normally distributed, can you conclude that the use of the
gasoline additive increases mileage at the 2.5% significance level?