The average gasoline price (µ) of one of the major oil companies in Europe has been $1.25 per liter with a population standard deviation of the population (σ) of $0.14. Recently, the company has undertaken several efficiency measures in order to reduce prices. Management is interested in determining whether their efficiency measures have actually reduced prices. A random sample of 49 of their gas stations is selected and the average price (x¯) is determined to be $1.20 per liter. What formula would you use to determine whether the new efficiency measures were effective? (a = 0.05)
F = s12 ÷ s22
t = (x¯ - μx-bar) ÷ s/√n
z = (x¯ - μx-bar) ÷ σ/√n
y = b0 + b1x