Let ?1 and ?2 denote true average densities for two different
types of brick. Assuming normality of the two density
distributions, test H0: ?1 ? ?2 = 0 versus Ha: ?1 ? ?2 ? 0 using
the following data: m = 7, x = 22.78, s1 = 0.164, n = 5, y = 21.92,
and s2 = 0.250. (Use ? = 0.05. Round your test statistic to three
decimal places and your P-value to four decimal places.)

t =

P-value =