Substitution in Eq. (17.2) (with renamed elements) yields t = (d - O)/sa =

1.58/(1.23/~) = 4.06. From Table II, the critical value for a 5% twotailed t with 9 dfis 2.26. Because 4.06 is much larger, we reject H0. Laevo, which has the larger mean, is more effective. From a statistical software package, p = 0.003.