Let X and Y equal the concentration of suspended particles in u(greek mu) g/m^3 in the cities of Melbourne and Houston respectively. Using n=13 observations of X and m=16 observations of Y, test H0: ux=uy against H1: ux<uy. (u represents mu)

a. define the test statistic and critical region, assuming that the unknown variances are equal . Let a(greek alpha)= 0.05

b. if x bar=72.9, sx(s subscript x)=25.6, y bar=81.7, sy=28.3, calculate the value of the test statistic and state your conclusion