Question

Two different formulas of an oxygenated motor fuel are being tested to study their road octane numbers. The variance of road octane number for formula 1 is σ12=1.5, and for formula 2 it is σ22=1.2. Two random samples of size n1=15 and n2=20 are tested, and the mean octane numbers observed are x¯1=89.0 fluid ounces and x¯2=92.2 fluid ounces. Assume normality.
a. Test the hypothesis that the formulations are equal versus the hypothesis that formulation 2 produces a higher mean road octane number than formulation 1. Calculate z0=
b. Calculate a 95% two-sided confidence interval on the mean difference road octane number.

Answer 1

Answer:

Step-by-step explanation:

a)

zo=(89.0-92.2)/sqrt((1.5/15)+(1.2/20))

zo=-8.00

p-value=0.0000

Reject the null hypothesis.

b)

95% confidence interval for difference

=(89-92.2)+/-1.96*sqrt((1.5/15)+(1.2/20))

=-3.2+/-0.78

=(-3.98, -2.42)