A device was installed to improve the gas mileage of

Question

1) Given 2 samples:

n₁ = 39      x₁^- = 10       s₁ = 1.4

 n₂ = 36     x₂^- = 9         s₂ = 1.25

a) Test if μ₁ = μ₂ with a one-tail at α = .05.

b) Do a 90% confidence interval.

2) Given 2 samples:

n₁ = 28      x₁^- = 50.1       s₁ = 3.9

n₂ = 25     x₂^- = 53.5       s₂ = 3.0

a) Test if μ₁ = μ₂ with a one-tail at α = .05.

b) Do a 90% confidence interval.

3) A device was installed to improve the gas mileage of vehicles in a small taxi fleet. Test whether the increase was statiscally significant with a two-tail test at α = .05.

Vehicle	Before	After
Car 47	15	16
Car 37	14	15
Car 22	13	15
Car 02	13	16
Car 10	12	13
Car 666	14	15