我印象中是z，请参考Tables referenced in MacKinnon, D.P., Lockwood, C.M., Hoffman, J.M., West, S.G., & Sheets, V. (in press, 2002). A comparison of methods to test mediation and other intervening variable effects. Psychological Methods.

z或t其实不重要，因为sobel检验已经被bootstrap法取代了。

我做的bootstrap出来的怎么也是t值--

bootstrap中的t值可以不用理会