[R-sig-ME] lme4: Obtaining the SE of difference in two fixed-effects

[Lenth, Russell V]

Do this:

    a <- c(0, 1, -1)
    V <- vcov(fit)
    sqrt(t(a) %*% V %*% a)

Russ


-----Original Message-----

Message: 2
Date: Wed, 28 Oct 2020 21:29:53 -0500
From: Simon Harmel <sim.harmel using gmail.com>
To: r-sig-mixed-models <r-sig-mixed-models using r-project.org>
Subject: [R-sig-ME] lme4: Obtaining the SE of difference in two
	fixed-effects slope
Message-ID:
	<CACgv6yVbsBJanYRLo4af7P=wUCLQn7RiyhPmE06sSVxNxbdF3Q using mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Dear All,

I'm interested in obtaining standard error (SE) of [*meanses - ses]* estimate
in my model below which serves as the contextual effect coefficient.

Is there a way to obtain this SE in R?

hsb <- read.csv('
https://raw.githubusercontent.com/rnorouzian/e/master/hsb.csv')

fit <- lmer(math ~ ses + meanses + (1|sch.id), data = hsb)

coef(summary(fit))

             Estimate Std. Error   t value
(Intercept) 12.661262  0.1493726 84.762956
ses          2.191165  0.1086673 20.163983
meanses      3.675037  0.3776607  9.731055