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After fitting a model with lme, I run post-hoc tests with glht (with specific hypotheses specified in ph_conditional, and not multiple comparisons). The results are repored in the following:

> lev.ph <- glht(lev.lm, linfct = ph_conditional);
> summary(lev.ph, test=adjusted("bonferroni"))

Simultaneous Tests for General Linear Hypotheses

Fit: lme.formula(fixed = data ~ des_days, data = data_red_trf, random = ~des_days |
    ratID, method = "ML", na.action = na.omit, control = lCtr)

Linear Hypotheses:
                Estimate  Std. Error  z value     Pr(>|z|)   
des_days1 == 0    3232.2      443.2     7.294     9.05e-13 ***
des_days14 == 0   3356.1      912.2     3.679     0.000702 ***
des_days48 == 0   2688.4     1078.5     2.493     0.038025 * 

I am trying to understand the output values. How are the z-scores computed? If the function uses standard errors, shouldn't these be t-statistics (and not z-scores)?

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