A comparison of the results from the present, Massachusetts, and Nova Scotia.

*P<0.05 indicates that a random-effects model is more appropriate.
Startum A = chlorinated and chloramined surface water; Stratum B = routine measurement of trihalomethanes; Startum C = excluded Taiwan study; Startum D = excluded England study; Startum E = focusing on routine measurement of trihalomethanes and excluded Taiwan study; Startum F = focusing on routine measurement of trihalomethanes and excluded England study; G = focusing on routine measurement of trihalomethanes and excluded both England and Taiwan studies; H = included England and Taiwan Studies.